Preheat the oven to 400F. Lightly fry the mushrooms, cap-side down, in hot oil for 20 seconds. Arrange the mushrooms in a shallow roasting tin with the stalks facing upwards. Mix together the butter, garlic,thyme, lemon juice and seasoning.
Spoon a little garlic butter on to each mushroom, then lightly press the breadcrumbs on top. Either refrigerate for later use, or cook immediately in the oven for 10 minutes.