In the bowl of a stand mixer, cream together butter and sugar. Add in eggs and sour cream, beating until well combined.
In a separate bowl, stir together flour, baking powder, and baking soda.
Gradually add dry mixture to wet mixture until well combined.
In a small bowl, stir together chocolate chips, brown sugar, cinnamon, and nutmeg. Gently add this to the batter with a large wooden spoon, being careful not to overmix.
Spread into a greased 9 x 13 baking dish. Bake at 350 degrees for 20 - 30 minutes or until a cake tester comes out clean.
Cool completely. Dust with powdered sugar before serving.