Preheat oven to 500°F. Mix cinnamon and nutmeg in small bowl. Prepare crusts as directed on package. Sprinkle spice mixture evenly on surface of each crust. Cut each crust into 4 equal pieces. Place 1 apple half in center of each piece of crust. Fill center of each apple half with 1 teaspoon of the butter. Carefully fold crust up over apple half, pinching seams together to seal. Place dumplings, seam-side down, in greased 13x9-inch baking dish.
Bring sugar, water and 2 tablespoons butter to boil in small saucepan. Remove from heat. Stir in vanilla; set aside.
Bake dumplings about 10 minutes or until crust begins to brown. Reduce oven temperature to 350°F. Pour sauce over dumplings. Bake 40 to 45 minutes longer or until apples are tender and pastry is golden brown. Serve warm with ice cream or whipped cream, if desired.