Preheat the oven to 350 degrees F (175 degrees C). Grease and flour a 10 inch Bundt pan.
Beat cake mix, sour cream, milk, oil, water, eggs, and pudding mix in a large bowl with an electric mixer for 4 minutes. Mix in 2 cups chocolate chips. Pour batter into the prepared pan.
Bake in the preheated oven until a toothpick inserted into the center of the cake comes out clean, 40 to 50 minutes. Cool in the pan for 10 minutes, then turn out onto a wire rack and cool completely.
Meanwhile, melt remaining 1 cup chocolate chips and butter in a double boiler or the microwave. Stir glaze until smooth, then drizzle over the cooled cake.
Chocolate Pudding Fudge Cake · Dinner Match Lab | Dinner Match Lab