Preheat the oven to 400F.
Lightly fry the mushrooms, cap-side down, in hot oil for 2-3 minutes.
Arrange the mushrooms in an oven-proof pan with the stems facing upwards.
In a small bowl, mix together the softened 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 bake immediately in the oven for 15 minutes or golden around the mushroom cap.