Preheat the oven to 350 degrees.
In the mixer bowl, combine sour cream, coffee, eggs, vegetable oil, and vanilla extract. Add the cake mix and mix for 2-3 minutes. Fold in the mini chocolate chips.
Pour the batter into a greased 9 x 13-inch pan and bake at 350 degrees for 30-35 minutes.
Allow the cake to rest for 20 minutes after baking.
In a small bowl, microwave peanut butter for 20 seconds or until smooth. Whisk in the condensed milk.
Using a fork or the back of a spatula, poke holes throughout the top of the cake. Pour the poke filling over the top. Cover the cake with plastic wrap or a lid and let it completely cool or refrigerate overnight.
In a mixer, cream butter and peanut butter for 2-3 minutes on medium speed. Slowly add in powdered sugar and milk. Once the mixture comes together, increase the speed to medium-high and whip for 3-4 minutes or until fluffy.
Spread the icing evenly over the cooled cake and top with chopped peanut butter cups.