Preheat your oven to 350°F (175°C). Grease and flour a 10–12 cup bundt pan thoroughly using softened butter or shortening, then dust with flour or cocoa powder, tapping out excess.
In a large mixing bowl, combine the devil’s food cake mix, instant chocolate pudding mix, sour cream, eggs, water, and vegetable oil. Blend with a hand mixer or whisk until smooth, about 2 minutes.
Fold in the chocolate chips with a spatula to ensure even distribution.
Pour the batter into the prepared bundt pan, smoothing the top. Bake for 45–50 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
Allow the cake to cool in the pan for 10 minutes. Run a butter knife gently around the edges to loosen, then invert onto a wire cooling rack. Cool completely, about 1 hour.
In a medium bowl, beat the softened cream cheese and butter with a hand mixer until light and fluffy, about 2 minutes. Add the vanilla extract.
Gradually mix in the powdered sugar, beating for 2–3 minutes until smooth and creamy. Adjust with more powdered sugar if thicker consistency is desired.
Spoon the frosting into a pastry bag or a ziplock bag with a corner snipped off. Starting at the outer edge of the cooled cake, pipe a line of frosting up and over the cake, toward the center hole. Repeat around the entire cake for a decorative drizzle.
Cover and refrigerate the cake for up to 5 days or freeze for up to 3 months. Thaw in the fridge overnight before serving.