Preheat the oven to 350 degrees F.
Grease a bundt pan very well with butter or nonstick spray. Use a small amount (like a teaspoon) of cocoa OR flour (Cocoa will be prettier) to dust the pan. Tap the pan around and shake out excess.
Combine the dry cake mix and dry pudding mix in a large bowl or stand mixer.
Beat in the sour cream, water, oil, and eggs. Scrape the sides and bottom and beat well for at least 2 minutes to whip air into the cake.
Fold in 2 cups of chocolate chips.
Pour the batter into the prepared pan and bake for 55-58 minutes, or until a toothpick comes out clean. Don't over bake it!!
Let cool on a wire rack for 10 minutes.
Use a plastic knife (so you don't scrape your pan) to loosen the edges of the cake, then invert it onto a serving plate or cake stand.
Meanwhile, make the ganache. In a small bowl, measure out 1 cup of cream. Microwave for about 1 minute, stir, and continue heating in 20 second intervals until you see bubbles on the side of the bowl.
Immediately pour in 1 cup chocolate chips but don't stir. Let the chocolate sit for about a minute (to melt) then use a whisk to stir it together. Don't give up, just keep whisking and it will thicken up.
Drizzle the warm cake with the ganache. You can serve it room temperature too, if you like. The ganache will thicken as it cools, just throw it in the microwave for a few seconds if you need it to thin out.
Garnish with mini chocolate chips and serve with a tall glass of cold milk!