1 (18.25 ounce) package white cake mix
1 (8 ounce) package cream cheese, softened
1 (3.4 ounce) package instant vanilla pudding mix
1 (3.4 ounce) package instant chocolate pudding mix
1 cup water
1/3 cup white sugar
4 eggs
2 1/2 cups sour cream
1 cup toasted, chopped pecans
1 cup confectioners' sugar
1 cup buttermilk
1 teaspoon vanilla extract
Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 10x15 inch pan. In a large bowl, stir together the cake mix and cream cheese. Set aside.
In a large bowl, stir together the pudding mix and pudding mix. Combine the water and 1/3 cup sugar; stir into the cake mixture. Stir in the eggs one at a time, then the flour mixture. Stir the batter until just moist. Pour into pan.
Bake for 35 to 40 minutes in the preheated oven, until a toothpick inserted into the center of the cake comes out clean. Let cool.
While the cake cool, frost it with confectioners' sugar and 1/2 cup buttermilk. In a medium bowl, beat the sour cream with the buttermilk until smooth. Spread over the cooled cake. In a medium bowl, pour the remaining 1 cup buttermilk over the entire cake, mixing just until combined. In another medium bowl, beat the confectioners' sugar with the vanilla until light and fluffy.