For the cake:

1. Preheat the oven to 325°F.
2. In a medium mixing bowl, add the cake mix, flour, eggs, butter, water, sour cream and dry pudding mix.
3. Using a hand mixer, mix until well combined, 2-3 minutes.
4. Gently fold in the mini chocolate chips.
5. Divided the batter evenly into lined cupcake pans - filling each cup 2/3 full.
6. Bake for 19 minutes.
7. Remove from the oven and let them cool in the pans for 5 minutes before moving to a cooling rack.

For the filling:

1. While the cupcakes are baking, cream the butter and brown sugar in a mixing bowl until light and fluffy.
2. Add the flour, sweetened condensed milk, and vanilla and continue to beat until smooth.
3. Stir in the mini chocolate chips.
4. Cover with plastic wrap or seal in an airtight container and refrigerate until the mixture has firmed up a bit. *I confess, I skipped the chilling. I put the filling into an icing bag with a large round tip (1A) and left it at room temperature until I used it. I’m not sure if or how it would’ve been better chilled.

For the frosting:

1. Cream the butter and brown sugar with a mixer (or paddle attachment) until light and fluffy.
2. Add the powdered sugar 1 cup at a time and mix on low until it’s all added.
3. Add the flour, salt, milk, and vanilla and mix until it’s all incorporated. I know flour might be a surprise ingredient (or at least it was for me), but this is really some of the very best frosting ever.
4. Mix or beat until super light and fluffy. It was so smooth… it was like it melted in my mouth!

Assembling the Cupcakes:

1. After the cupcakes have cooled, you can use an apple corer (mine is Tupperware) to easily pop out a hole in the middle of the cupcakes to prep them for filling.  If you don't have an apple corer, see another option below.
2. Next, pipe the cookie dough filling into the hole to fill in where you scooped out the cake, and smooth it down with your finger if needed.
3. Pipe the frosting on top of the cupcake with a 1M tip or similar.
4. Sprinkle with mini chocolate chips.

Alternately, you could also just cut a chunk of cake out of the center with a knife if you wanted to and fill it with a spoon, but the tools make it a little easier & neater!