Place your ovenproof skillet in the oven and preheat to 450°F for 25 minutes. (see Note 2)
In a small bowl add the flour, cornstarch, salt and pepper. Set aside.
In a blender add the eggs, milk and 2 tablespoons of melted butter, blend for 10 seconds. Add the flour mixture and blend for 30 seconds.
CAREFULLY remove skillet from oven and add remaining tablespoon of butter, swirl to coat bottom. Pour egg mixture in skillet and immediately sprinkle a quarter cup each of the cheese and pesto on the top.
Bake for 20 minutes, until puffy and sides are golden brown.
Remove from oven and top with remaining cheese, pesto and the prosciutto. Serve immediately.
1. Prosciutto thinly sliced, usually about 3-4 slices. Tear into bite size pieces. 2. Cast iron skillets work best I think, just make sure your skillet is safe to put in the oven.