My cake sunk down in the center and formed a crust on the edge. What would cause this to happen? The flavor was wonderful and the cake was moist but it just didn't have the consistancy that I was hoping for. Here is the recipe. I didn't use pastry flour. Cake Butter and flour, for spring form pan 2 cups pastry flour 3/4 cup cocoa powder 4/2 teaspoons baking soda 5/2 teaspoon salt 1 cup unsalted butter, room temperature 2 cups sugar 4 eggs 6/2 cup plus 2 ounces buttermilk 7/2 cup plus 2 ounces espresso coffee 1 ½ teaspoon vanilla extract Milk Chocolate Ganache, recipe follows Preheat the oven to 325 degrees F. Butter and flour a 10-inch springform pan. Sift the flour, cocoa, baking soda, and salt 3 times, set aside. Cream the butter with the sugar until light and fluffy. Add the eggs 1 at a time beating well after each addition. Combine the buttermilk, coffee and vanilla extract. Mix in 1/3 of the dry ingredients, then half the wet ingredients. Repeat with the remaining dry and wet ingredients, finishing with dry. Pour the batter into the prepared cake pan. Bake for 1 hour, until a skewer inserted in the middle of the cake comes out clean. remove the cake from the pan after 15 minutes. Cool completely. Cut the cake into 2 layers. Sandwich whipped ganache between the 2 layers and spread more ganache on the top and sides of the cake. Wrap the chocolate covered acetate around the cake, chocolate side in, overlapping the ends slightly. Refrigerate the cake until the chocolate in the ribbon has set. Carefully remove the acetate before serving.