Clean the mushrooms, possibly wash and halve them. Peel and chop the garlic. Wash thyme, shake dry, remove leaves.
Preheat the oven grill. Spread the breads on a baking tray lined with baking paper. Roast under the grill for 1-2 minutes, turn, cover with cheese and bake until golden brown. Fry mushrooms in hot oil, season with salt and pepper.
Add butter, garlic, thyme and lemon peel and let the butter foam once. Spread on the breads.