Preheat the oven to 400 F. Line a 12-cup muffin pan with paper liners. Sift the flour, cocoa, baking powder, and baking soda into a large bowl. Add the semisweet and white chocolate chips, and stir.

Place the eggs, sour cream, sugar, and melted butter in a separate mixing bowl, and mix well. Add the wet ingredients to the dry ingredients, and stir gently until just combined.

Using two spoons, divide the batter evenly among the paper liners. Then bake in the preheated oven for 20 minutes, or until well risen and firm to the touch. Remove from the oven and serve warm, or place on a cooling rack and let cool.