1Butterfly chicken breasts and grill over hot coals for 3-5 minutes per side, or until cooked through.
Remove from grill and allow to cool.
2Holding a breast in your hand, opened like a taco shell, stuff each breast with one slice of prosciutto and 1/8 cup Fontina cheese.
Secure breasts closed with toothpicks. Set aside and keep warm.
3In a large skillet over medium heat, sauté garlic and onion in clarified butter until tender.
Deglaze pan with wine.
Add mushrooms, butter, salt, and pepper and sauté 1-2 minutes, or until mushrooms are tender.
Stir in basil and lemon juice.
Top stuffed chicken with prepared sauce.
4NOTE: To make clarified butter, melt butter over low heat; remove from heat and let sit until the milk solids settle to the bottom; skim the clear butter from the top; discard sediment.