- Preheat oven to 450°.
- Heat a 12-inch nonstick skillet over medium-high heat.
- Coat pan with cooking spray. Add mushrooms and shallots to pan; sauté 7 minutes or until mushrooms are tender.
- Add garlic and thyme; sauté 1 minute. Stir in vinegar; remove from heat.
- Place crust on the bottom rack of oven. Bake at 450° for 4 minutes.
- Place the crust on a baking sheet. Spread mushroom mixture evenly over crust; sprinkle evenly with prosciutto and fontina cheese. Bake at 450° for 6 minutes or until cheese melts.