Roasted Flat Mushrooms with Green Onion, Thyme & Butter is a delightful dish that highlights the rich flavor of mushrooms combined with fresh herbs and creamy butter. This recipe is simple yet elegant, making it perfect for both weeknight dinners and special gatherings. It showcases how basic ingredients can come together to create something truly delicious.

Why Make This Recipe
There are many reasons to make Roasted Flat Mushrooms. Firstly, mushrooms are packed with nutrients and add a wonderful umami flavor to any dish. This recipe is also quick to prepare, taking only about 30 minutes from start to finish. Using fresh green onions and thyme adds a bright and aromatic touch that enhances the overall taste. Plus, it looks beautiful on the plate, making it an impressive side dish or appetizer.
How to Make Roasted Flat Mushrooms with Green Onion, Thyme & Butter
Ingredients
- 8 large flat mushrooms (portobello, around 10 – 12 cm / 4 – 4.5″ wide, stem tips trimmed)
- 100g / 7 tbsp unsalted butter (softened)
- 1 cup green onion (thinly sliced)
- 1/3 cup parsley (finely chopped)
- 1 tbsp fresh thyme leaves (or 1 tsp dried)
- 1/2 tsp salt
- 1/4 tsp black pepper
- 3 tbsp chopped scallions
- 1 dozen thyme stalks
Directions
- Clean mushrooms: Start by cleaning the mushrooms as per Note 1.
- Preheat oven: Preheat your oven to 200°C (390°F) or 180°C (fan).
- Mix butter: In a medium bowl, mix together the softened butter, green onions, parsley, thyme, salt, and pepper.
- Smear mushrooms: Place the mushrooms gills side up on a large tray. Use the butter mixture to smear over the surfaces of the mushrooms. Cover the tray with foil to keep the herbs green.
- Bake: Bake in the oven for about 25 minutes, or until the mushrooms are tender.
- Serve: Arrange the mushrooms on a platter, pouring any leftover butter and juices from the tray over them. Scatter with thyme stalks and extra scallions for a fresh touch before serving.
How to Serve Roasted Flat Mushrooms
Roasted Flat Mushrooms are best served warm and can be enjoyed on their own or as a side dish. They pair well with grilled meats, salads, or even pasta. Garnishing them with extra scallions and thyme adds a lovely presentation, making them eye-catching for your guests.
How to Store Roasted Flat Mushrooms
If you have leftovers, allow the mushrooms to cool to room temperature. Place them in an airtight container and store them in the refrigerator. They can be kept for up to 3 days. Reheat gently in the oven or microwave before serving again.
Tips to Make Roasted Flat Mushrooms
- Ensure mushrooms are cleaned gently to avoid using too much water, which can make them soggy.
- You can adjust the herbs according to your preference. Try adding more parsley or even some garlic for additional flavor.
- For a vegan option, substitute the butter with plant-based margarine.
Variation
For a twist on this dish, consider adding cheese on top of the mushrooms before baking. A sprinkle of goat cheese or grated Parmesan can add richness and depth to the flavor.
FAQs
1. Can I use smaller mushrooms for this recipe?
Yes, smaller mushrooms can be used. Just adjust the baking time as smaller mushrooms might cook faster.
2. What can I serve with these mushrooms?
These mushrooms work well as a side dish alongside grilled meats, in salads, or as a topping for toasted bread.
3. Can I freeze Roasted Flat Mushrooms?
While it’s best to enjoy them fresh, you can freeze them. However, the texture may change upon reheating, so it’s not recommended for long-term storage.
Enjoy making Roasted Flat Mushrooms with Green Onion, Thyme & Butter, and savor the delicious flavors that come from these simple ingredients!

Roasted Flat Mushrooms with Green Onion, Thyme & Butter
Ingredients
Mushrooms
- 8 large large flat mushrooms (portobello, around 10 – 12 cm / 4 – 4.5″ wide, stem tips trimmed)
Butter and Seasoning
- 100 g unsalted butter (softened) About 7 tablespoons
- 1 cup green onion (thinly sliced)
- ⅓ cup parsley (finely chopped)
- 1 tbsp fresh thyme leaves (or 1 tsp dried)
- ½ tsp salt
- ¼ tsp black pepper
- 3 tbsp chopped scallions
Garnish
- 1 dozen thyme stalks
Instructions
Preparation
- Start by cleaning the mushrooms as per Note 1.
- Preheat your oven to 200°C (390°F) or 180°C (fan).
- In a medium bowl, mix together the softened butter, green onions, parsley, thyme, salt, and pepper.
Baking
- Place the mushrooms gills side up on a large tray. Use the butter mixture to smear over the surfaces of the mushrooms.
- Cover the tray with foil to keep the herbs green.
- Bake in the oven for about 25 minutes, or until the mushrooms are tender.
Serving
- Arrange the mushrooms on a platter, pouring any leftover butter and juices from the tray over them.
- Scatter with thyme stalks and extra scallions for a fresh touch before serving.







