Prepare the piecrusts as described on page 9. Roll out the 2 disks of dough and fit them into 9-inch pie pans. Crimp the edges. Refrigerate the piecrusts for at least 30 minutes. Preheat the oven to 350?F. Line the piecrusts with parchment paper or aluminum foil and fill each with pie weights. Bake until the crusts just set, about 20 minutes. Remove from the oven and remove weights. Allow to cool.
Preheat the oven to 350?F.
Combine the milk, water, 1 teaspoon salt, garlic, and bay leaves in a large saucepan over medium-high heat. Once the mixture is hot, add the potatoes and gently stir to combine. Bring to a boil and cook, stirring occasionally, until the potatoes are tender, about 8 minutes. Drain the potatoes (the cooking liquid may be reserved to form the base of a soup).
Line each of the baked piecrusts with half of the potatoes. Cover the potatoes with the cubed ham. Pour 1/4 cup cream on top of the potatoes in each pie. Sprinkle 1/4 cup Gruyere and 1/4 cup Parmesan on top of the cream in each pie. Arrange 1 tablespoon butter on top of the cheese in each pie. Arrange the remaining half of the potatoes on top of the creamy mixture. Sprinkle 1/2 teaspoon thyme on top of the potatoes in each pie. Pour 1/2 cup of the remaining cream over each pie. Dot each pie with 1 tablespoon of the remaining butter. Sprinkle 1/4 cup Gruyere and 1/4 cup Parmesan on top of each pie. Sprinkle each pie with 1/4 teaspoon salt and 1/4 teaspoon black pepper. Bake the pies until golden brown and bubbly, about 30 minutes.
Makes two 9-inch pies, 8 to 10 servings