In a large bowl, stir together cake mix, pudding mix, eggs, water, milk, and oil.
Line 24 regular-sized muffin cups with paper liners.
Fill muffin cups halfway with batter.
Bake at 350 degrees for 15-20 minutes, or until tops appear set, and a toothpick inserted near the center comes out clean.
Remove to wire racks to cool completely.
Using a teaspoon or small spoon (a grapefruit spoon works best!), hollow out a 1-inch ball in the center of each cupcake. Set aside cake crumbs for another use (cake balls, maybe?).
Spoon a rounded teaspoonful of Nutella into the center of each cupcake. The easiest way to do this is with a small cookie scoop!