Apple, Onion and Prosciutto di Parma Tart - Prosciutto Di Parma

Ingredients

• 1 1/4 cups flour
• 1/2 teaspoon salt
• 1/2 teaspoon sugar
• 1 stick cold unsalted butter, cut into small pieces
• 2 to 4 tablespoons ice water
• 3 tablespoons unsalted butter
• 2 Gala apples, peeled, cored and sliced
• 1 yellow onion, sliced thin
• 1/2 teaspoon fresh rosemary leaves
• 4 medium sage leaves, chopped
• 6 ounces thinly-sliced Prosciutto di Parma, cut into thin strips
• 3 tablespoons dry white wine
• 1 batch Rich Pie Pastry (see recipe)
• 1/3 cup ricotta cheese
• 3 ounces Gorgonzola dolce, diced
• 1 egg yolk
• 2 tablespoons heavy cream
• Freshly ground black pepper, to taste