Preheat oven to 375°F (190°C).
Flatten chicken breasts slightly and coat with melted butter, then dredge in Italian breadcrumbs.
In a skillet, melt butter and whisk in flour to make a roux.
Slowly stir in chicken stock, white wine, and lemon juice. Simmer until thickened.
In a baking dish, place breaded chicken, pour sauce over it.
Top with sliced mushrooms, prosciutto, and shredded Provel cheese.
Bake uncovered for 20–25 minutes or until golden and bubbly.
Let rest for a few minutes before serving.