Step 1

Preheat oven to 350 degrees F.

Step 2

Line a 9-inch x 9-inch pan with parchment paper & spray with cooking spray.

Step 3

Combine cake mix, butter, and egg in a stand mixer bowl. Beat with the paddle attachment until it forms into a thick dough. (You can also use an electric hand mixer.)

Step 4

Press 2/3 of the dough into the prepared baking pan- it will look like there isn't enough to cover the bottom, just keep working it into a thin even layer. It will cover the bottom.

Step 5

Sprinkle with 1/2 cup of each type of chocolate chips over the dough.

Step 6

Pour sweetened condensed milk over the top in a thin, even coating.

Step 7

Separate remaining dough into balls, and evenly distribute over the top of the chocolate chips.

Step 8

Press dough balls down to flatten a bit.

Step 9

Sprinkle with remaining chocolate chips.

Step 10

Bake for 27- 30 minutes until the top is set.

Step 11

Remove from oven and cool completely before slicing... if you aren't eating warm, right out of the pan.