Preheat the oven to 350°F (177°C) and generously grease a 9×5-inch loaf pan.

Whisk the flour, baking powder, and salt together. Set aside.

Using a handheld or stand mixer fitted with a paddle or whisk attachment, beat the butter and sugar together on medium-high speed until smooth and creamy, about 3 minutes. (Here’s a helpful tutorial if you need guidance on how to cream butter and sugar.) Scrape down the sides and up the bottom of the bowl with a silicone spatula as needed. Add the eggs and beat on high speed for 1 minute, then beat in the sour cream and vanilla extract. Scrape down the sides and up the bottom of the bowl as needed. The mixture will be very lumpy and appear curdled—that’s ok. Pour the dry ingredients into the wet ingredients. Turn the mixer to low speed and as the mixer runs, slowly pour in the milk. Beat on low speed just until all of the ingredients are combined. Do not over-mix. You may need to whisk it all by hand to make sure there are no large lumps at the bottom of the bowl. The batter will be slightly thick. Gently fold in the chocolate chips.

Pour and spread batter evenly into prepared loaf pan.

Bake for about 60-75 minutes or until a toothpick inserted in the center comes out clean. That time is a guideline—all ovens differ, so keep a close eye on the cake after 55 minutes. If the cake is browning too quickly on top, loosely tent with aluminum foil as it bakes.

Cool cake in the pan set on a wire rack for at least 1 hour before removing from the pan. Feel free to continue cooling it directly on a wire rack or slice and enjoy then. (It will still be slightly warm.) You can drizzle the topping on the cake when the cake is still slightly warm after that 1 hour of cooling or wait until the cake has cooled completely to top it.

Stir and melt chocolate chips and peanut butter together in a small saucepan over medium heat on the stove or in a heatproof bowl using the microwave. We usually use the microwave and melt in 30 second increments, stirring after each until smooth. Drizzle over cake. Topping sets into a fudge-like consistency after several hours.

Cover leftovers tightly and store cake (with or without topping) at room temperature for 3 days or in the refrigerator for up to 1 week.