The crumbly coconut-pecan mixture goes both inside the cake and on top of it to make this dessert.
Grease and flour a 9-inch springform pan; set aside. In a large mixing bowl, beat butter with an electric mixer on medium to high speed for 30 seconds. Add the sugar, baking powder, baking soda, and salt. Beat until well combined, scraping sides of bowl occasionally. Add eggs, 1 at a time, beating well after each addition. Beat in vanilla. Alternately add flour and sour cream to butter mixture, beating on low speed after each addition just until combined.
Spread half of the cake batter into prepared pan. Sprinkle with half of the Coconut Pecan Topping. Spoon remaining cake batter in mounds over coconut mixture. Carefully spread to an even layer. Sprinkle with remaining Coconut Pecan Topping.
Bake in a 350 degree F oven about 65 minutes or until a long wooden skewer inserted near the center comes out clean. If necessary, cover cake with foil for the last 15 to 20 minutes of baking to prevent overbrowning. Cool on a wire rack for 20 minutes. Run a thin metal spatula around edge of cake. Remove sides of the pan. Cool about 30 minutes more. Serve warm.
In a large bowl combine flour, brown sugar and cinnamon. Cut in cold butter until mixture resembles coarse crumbs; stir in semisweet chocolate pieces, coconut, and pecans.