Step 1

Preheat oven to 400°F/200C.

Step 2

Wipe the portobello mushrooms clean and remove the stems. Finely chop or mince the garlic.

Step 3

Lightly oil a baking dish or baking sheet and put the mushrooms on top in a single layer, open side up.

Step 4

In a small bowl, mix together the oil, garlic, thyme, and a little salt and pepper. Divide the mixture between the mushrooms, drizzling over the inside. Top each with a thin slice of butter.

Step 5

Bake the mushrooms for around 15 minutes until tender.

Step 6

While they are cooking, mix together the cheeses. After the 15 min, top the mushrooms with the cheese and return to the oven for around 5 minutes until the cheese is melted and gently golden.