I am an amateur cook. I have been making a wonderful cake for years. It has been reliable under all kinds of conditions and even rather laissez-faire measuring methods. Suddenly today both layers came out dramatically sunken in the middle. I will include the recipe below. The baking soda is not past date. I am baffled. Help please! It's a wonderful cake. Cake (this is from Bon Appetite about 10 years ago) (1 recipe fills 1 round 14" X 2" pan or 2 round 9" X 2" pans) 2 C espresso, room temp 3C sifted cake flour 2/3 C plus 4 tsp sifted unsweetened cocoa powder 2 tsp baking soda 1 tsp salt 1/2 tsp (generous) baking powder 1C (2 sticks) unsalted butter, room temp 3 C sugar 4 large eggs, room temp 2 oz. unsweetened chocolate, chopped, melted, cooled to barely lukewarm Preheat oven to 325degrees F. Butter 4 cake pans (9" round). Butter bottom and sides of the pan. Line bottom and sides with parchment paper. Butter and flour paper. Sift flour, cocoa, baking soda, salt and baking powder into a medium bowl. In a large bowl, using electric mixer, cream butter until light. Gradually add sugar and beat until fluffy. Add eggs one at a time and beat just until combined. Add melted chocolate and beat until just blended. Mix dry ingredients and espresso liquid alternately into batter, beginning and ending with dry ingredients. Divide batter among the pans (half full). Bake until tester inserted in center of cake comes out clean. Cool cakes in pans on racks. Wrap in foil or plastic wrap and freeze or refrigerate over night.