To prepare a stuffed fillets of sole with mushroom sauce appetizers recipe, you'll first need to prepare the ingredients for the appetizer. Cut the sole into 12 inch thick slices. Place the slices in the microwave-safe bowl and microwave for 30 seconds, or until they're heated through. Remove from microwave and set aside to cool. To make the filling, mix together the ricotta cheese, parsley, thyme, salt, pepper, and paprika. Spread the cheese mixture evenly over the top of each slice of fleshy sole. Top with the mushrooms and serve.