Preparation Steps

• Preheat the oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan or line it with parchment paper.
• In a large mixing bowl, combine the yellow cake mix and instant vanilla pudding mix until evenly blended.
• Add the eggs, sour cream, vegetable oil, 0.5 cup melted butter, and vanilla extract. Beat on medium speed until smooth and no dry streaks remain, about 2 to 3 minutes.
• Fold in the mini chocolate chips by hand, reserving a few to sprinkle on top if desired.
• Spread the batter evenly into the prepared 9x13 pan. Smooth the top with a spatula.
• Bake in the preheated oven for 22 to 28 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs. Avoid overbaking to keep the cake moist.
• While the cake bakes, prepare the glaze: whisk together the remaining 0.5 cup melted butter, powdered sugar, and milk until smooth. Adjust milk to reach a pourable but thick glaze.
• When the cake is done, let it cool in the pan for 10 minutes. Poke holes all over the warm cake with the handle of a wooden spoon or a skewer.
• Pour the glaze evenly over the warm cake, allowing it to sink into the holes. Sprinkle the reserved mini chocolate chips on top.
• Let the cake cool completely before slicing so the glaze sets. Store covered at room temperature for up to 3 days.