Preheat your oven to 350 degrees F. Spray three 8-inch or four 6-inch round pans with nonstick spray, line the bottoms with parchment paper, and spray again. Set aside.
In a large bowl, mix together the cake and pudding mixes, sour cream, oil, beaten eggs, and water. Stir in the chocolate chips and pour batter into your prepared pans.
Bake for 18-20 minutes (you may need more time depending on your oven), until toothpick comes out with just a few moist crumbs on it. Cool on wire racks for 10-15 minutes, then gently invert onto racks until cooled completely.
Preheat the oven to 350°F. Line 2 cupcake pans with 16 cupcake liners.
In the bowl of a stand mixer fitted with the paddle attachment, mix the dry ingredients on low speed for 1 minute until combined.
In a measuring cup, whisk together the wet ingredients. With the mixer on low speed, slowly pour the buttermilk mixture into the bowl and mix until just combined. Add the sour cream and mix on
medium-high speed for 2 minutes. Scrape down the sides of the bowl and continue mixing for 10 to 15 seconds. The batter will look thin and runny.
Divide the batter evenly among the cupcake liners, filling each three-quarters full. Bake for 15 to 18 minutes, or until a toothpick inserted in the middle of a cupcake comes out clean. Let cool for 5 minutes in the pans before transferring the cupcakes to a wire rack to cool completely.
Preheat your oven to 350 degrees F. Spray three 8-inch or four 6-inch round pans with nonstick spray, line the bottoms with parchment paper, and spray again. Set aside.
In a measuring cup, whisk together the wet ingredients. With the mixer on low speed, slowly pour the buttermilk mixture into the bowl and mix until just combined. Add the sour cream and mix on medium-high speed for 2 minutes. Scrape down the sides of the bowl and continue mixing for 10 to 15 seconds. The batter will look thin and runny.
Divide batter evenly among prepared pans (I like to use a kitchen scale to ensure the batter is evenly distributed - should be about 16 ounces of batter in each 8-inch pan or 12 ounces for each 6-inch).
In the bowl of a stand mixer fitted with the whisk attachment, whip the butter on low speed for 30 seconds. Increase the speed to high and whip for 2 minutes. Reduce the speed to medium and add the icing sugar. Whip for an additional 30 seconds. Add the peanut butter to the buttercream. Whisk on medium-high speed until well combined.Increase the speed to high and whip for 2 minutes, until the mixture looks light and fluffy. Scrape down the sides of the bowl. Add the vanilla bean paste and whip on high speed for 1 minute. 2. Use immediately or store in an airtight container in the fridge for up to 2 weeks. Remove from the fridge 1 hour before using.