Miso butter mushrooms turn a handful of fresh mushrooms into a warm Japanese side dish with very little washing up. Want tender mushrooms, sweet onion and a savory sauce you can spoon over rice? A sealed foil packet brings those flavors together in the oven.
Konnichiwa, I’m Hana. Let’s prepare two parcels with thin onion and a smooth miso sauce. The mushrooms cook in their own juices; five photos show each stage.
Table of Contents
Miso Butter Mushrooms Overview
Makes 2 foil packets for 4 side servings. Preheat the oven while preparing; add a few minutes if needed.
This recipe makes four side servings from two foil packets. Each packet holds 250 g mushrooms and 50 g onion, so half a packet is one side serving. For a larger meal, serve one packet per person with rice and another dish.
Allow about 10 minutes to prepare and 20 minutes to bake. Start preheating before chopping; dense packets may need extra time.
What Is Kinoko no Hoiru Yaki?
Kinoko means mushrooms; hoiru yaki describes cooking in foil. The packet holds moisture around the food, giving the mushrooms a soft, juicy texture. Japanese home-cooking references such as Marukome’s mushroom foil dish also use this simple technique.
Here, miso adds savory depth, butter rounds out the sauce and onion becomes gently sweet underneath. There is no cream in the recipe. Expect a small pool of mushroom juices mixed with melted butter, rather than a thick sauce or crisp, pan-fried mushrooms.
Ingredients for Miso Butter Mushrooms
Mixed mushrooms — 500 g
The photos use 100 g each of shiitake, shimeji, maitake, enoki and king oyster. A mix gives you different shapes and textures. You can use fewer varieties; keep the total weight at 500 g and cut larger pieces so they cook evenly.
Onion — 100 g
Slice yellow onion about 2 mm thick. Thin crescents soften beneath the mushrooms; thick chunks need longer. Weigh the prepared onion so both packets get an even base.
Miso and sake
Mix 2 tablespoons white or mild awase miso, about 36 g, with 2 tablespoons sake, 30 ml. Miso brands differ in saltiness. Unsalted vegetable stock can replace the sake when you want an alcohol-free version.
Butter and the finishing touches
Use 20 g unsalted butter: one 10 g piece per packet. Keep 1 teaspoon soy sauce, 5 ml, optional for after cooking. Finish with 2 tablespoons sliced green onion if you like. No extra salt is needed at the start.
Ingredient Substitutions
When Japanese mushrooms are hard to find
Use cremini, ordinary oyster mushrooms or sliced portobello in place of some of the mix. Keep 500 g total. Remove tough stem parts and cut thick pieces smaller; very large chunks can stay firm while the onion cooks.
Adjust the miso and butter
For stronger red miso, start with 1½ tablespoons, about 27 g, and omit the optional soy sauce until tasting. Salted butter also adds salt. For a dairy-free version, use 20 g plant-based butter.
Check dietary labels
For a vegan version, choose miso without fish-derived dashi and use vegetable stock. For gluten-free needs, check the miso ingredients and replace the finishing soy sauce with verified gluten-free tamari. Cooking sake does not guarantee that all alcohol disappears.
How to Make Miso Butter Mushrooms in 5 Steps
Prepare the tray and foil before building the packets. The amounts below are for both packets together; divide them evenly. Use the conventional oven setting or the lower fan setting, rather than a grill or broiler.
Step 1: Prepare the mushrooms and onion
Preheat the oven to 220°C / 425°F (200°C / 390°F fan). Slice the onion 2 mm thick. Trim woody shiitake stems and the compact bases of shimeji, maitake and enoki. Separate clusters, cut enoki to about 5 cm and slice shiitake and king oyster into bite-size pieces.
Brush off visible dirt or rinse briefly, then pat dry. Separate the clumps so heat can reach the middle.
Step 2: Mix the miso sauce
Stir 2 tablespoons miso with 2 tablespoons sake until smooth. Use unsalted vegetable stock instead of sake for an alcohol-free version. The butter and optional soy sauce are added separately.
Break up miso lumps against the bowl. Keep the optional soy sauce aside until after cooking.
Step 3: Build two even foil packets
Cut two sheets of heavy-duty foil, each about 36 × 40 cm (14 × 16 inches). Divide the onion between the centers, then add half the mushrooms to each. Spoon half the miso mixture over each mound and top each with 10 g butter. Leave space around the food for folding.
Spread even mounds over the onion base. Leave plenty of bare foil for folding.
Step 4: Seal and bake
Bring the long edges together above the mushrooms and fold them down twice; fold both ends closed, leaving a little headroom. Set both packets seam-side up on a rimmed baking tray. Bake on the middle rack for about 20 minutes. Carefully check that the mushrooms are thoroughly cooked and tender and the onion is soft. Reseal and cook 3–5 minutes longer if needed.
Cook enoki thoroughly before eating, as advised by the Singapore Food Agency.
Step 5: Open, season and serve
Move the tray onto a heatproof surface. Use oven mitts and open each packet away from your face to release steam. Gently toss the mushrooms with their juices. Taste, then divide up to 1 teaspoon soy sauce between both packets if needed. Add green onion and serve hot, allowing half a packet per side serving.
Share the juices too: their miso flavor makes a savory topping for plain rice.
Hana’s Tips for Tender Mushrooms
Keep the parcels similar in size
Divide the mushrooms evenly, fold the seams firmly and leave a little room above the food. Loose seams let the cooking moisture escape. If the foil tears, wrap that packet in a fresh sheet.
Taste before adding soy sauce
Miso already brings salt. Toss the cooked mushrooms with the juices first, then add the finishing soy sauce only if needed. Start with a few drops rather than the whole teaspoon.
Use the juices wisely
A little liquid is normal because mushrooms release moisture. Serve it with rice. If a packet is too watery, lift the mushrooms into a bowl and spoon over only as much liquid as you want.
Recipe Variations
Spicy finish
Add a little shichimi togarashi at the table. The main photos show the green onion version.
A brighter bowl
Finish with a few drops of lemon or yuzu juice, then taste before adding soy sauce.
A simple rice topping
Divide the mushrooms and juices over warm rice for two light bowls. Serve cooked tofu separately for a larger meal.
Storage and Make-Ahead Tips
Trim the mushrooms and slice the onion ahead, keeping them covered and refrigerated. Store the sauce separately; assemble close to baking.
Transfer leftovers out of the foil into shallow covered containers and refrigerate within two hours, or one hour when the surroundings are above 32°C / 90°F. Keep at 4°C / 40°F or colder and use within 2–3 days. This follows the cooling principles in FoodSafety.gov’s storage guidance.
Reheat only the amount you need until it reaches 74°C / 165°F, using the official leftovers temperature guidance. A covered pan or microwave-safe bowl works well. Remove all foil before microwaving.
Serving Ideas and Related Recipes
Serve the mushrooms beside steamed rice, a crisp salad and a simple main dish. The sauce is rich, so smaller side portions work well. For another mushroom meal or a fish pairing, try these JapanDishes recipes.
Another warm meal built around mushrooms.
A main dish to serve beside your mushroom packets.
Miso Butter Mushrooms in Foil きのこのホイル焼き
Course: Side dishCuisine: JapaneseDifficulty: Easy4
side servings10
minutes20
minutes30
minutesIngredients
500 g mixed fresh mushrooms (for example, 100 g each of shiitake, shimeji, maitake, enoki and king oyster)
100 g yellow onion, sliced 2 mm thick
2 tablespoons white or mild awase miso (about 36 g)
2 tablespoons sake (30 ml; or unsalted vegetable stock for an alcohol-free version)
20 g unsalted butter, divided into two 10 g pieces
1 teaspoon soy sauce (5 ml), optional, divided after cooking
2 tablespoons thinly sliced green onion, optional, for serving
Directions
- Preheat the oven to 220°C / 425°F (200°C / 390°F fan). Slice the onion 2 mm thick. Trim woody shiitake stems and the compact bases of shimeji, maitake and enoki. Separate clusters, cut enoki to about 5 cm and slice shiitake and king oyster into bite-size pieces.
- Stir 2 tablespoons miso with 2 tablespoons sake until smooth. Use unsalted vegetable stock instead of sake for an alcohol-free version. The butter and optional soy sauce are added separately.
- Cut two sheets of heavy-duty foil, each about 36 × 40 cm (14 × 16 inches). Divide the onion between the centers, then add half the mushrooms to each. Spoon half the miso mixture over each mound and top each with 10 g butter. Leave space around the food for folding.
- Bring the long edges together above the mushrooms and fold them down twice; fold both ends closed, leaving a little headroom. Set both packets seam-side up on a rimmed baking tray. Bake on the middle rack for about 20 minutes. Carefully check that the mushrooms are thoroughly cooked and tender and the onion is soft. Reseal and cook 3–5 minutes longer if needed.
- Move the tray onto a heatproof surface. Use oven mitts and open each packet away from your face to release steam. Gently toss the mushrooms with their juices. Taste, then divide up to 1 teaspoon soy sauce between both packets if needed. Add green onion and serve hot, allowing half a packet per side serving.
Notes
- Makes 2 packets / 4 side servings. Conventional oven: 220°C / 425°F; fan: 200°C / 390°F. Check tenderness at 20 minutes and bake longer if needed. Soy sauce is optional after tasting. Replace sake with unsalted vegetable stock for an alcohol-free version. Cook enoki thoroughly. Remove foil before microwaving leftovers.
Frequently Asked Questions
Can I use only one kind of mushroom?
Yes. Keep 500 g total and cut thick pieces smaller. The texture will differ from the five-variety photos.
Why is my onion still firm?
Thick slices, crowding or a cool oven can cause this. Reseal and bake longer; use thin onion next time.
Should I add water inside the foil?
No. Sake or stock moistens the miso, and the mushrooms release juices. Extra water makes the sauce thinner.
Can I double the recipe?
Yes. Make four even packets. Leave space on the trays; a crowded oven may need extra cooking time.
Bring the warm mushrooms to the table and let everyone spoon a little miso butter sauce over their rice. Itadakimasu!