Preheat oven to 350°F (175°C). Spray a 9x13-inch baking dish with nonstick baking spray. If using plain spray without flour, dust lightly with cocoa powder after spraying.
In a large mixing bowl, combine the dry Devil's Food cake mix and the dry instant chocolate pudding mix. Whisk together to distribute evenly.
In a separate small bowl, whisk together the eggs, sour cream, vegetable oil, warm water, and vanilla extract until just combined.
Pour the wet mixture into the dry ingredients. Using a hand mixer on low speed, mix for 30 seconds until incorporated, then increase to medium and beat for 2 full minutes. Scrape down the sides and bottom of the bowl.
Gently fold in 1 cup of semi-sweet chocolate chips with a rubber spatula, using slow sweeping motions about 8 to 10 times until evenly distributed.
Transfer the thick batter to the prepared pan and spread evenly. Tap the pan on the countertop a few times to release air bubbles.
Bake on the center rack for 32 to 38 minutes, checking at 32 minutes with a toothpick. The cake is done when the toothpick comes out with a few moist crumbs, not wet batter.
Remove from the oven and let cool in the pan on a wire rack for at least 30 minutes before adding the ganache.
For the ganache, combine ½ cup of semi-sweet chocolate chips and ¼ cup of heavy cream in a small saucepan over low heat, stirring constantly for 3 to 4 minutes until smooth. Do not boil. Alternatively, microwave in 20-second intervals, stirring between each.
Let the ganache cool for 2 to 3 minutes, then pour evenly over the cooled cake. Spread to the edges if needed. Allow to set for 10 to 15 minutes before slicing.