Make the brownies according to directions on the box and bake as directed. Let cool.
To make the cookie dough, cream together the butter, brown sugar, granulated sugar and vanilla until light and fluffy. Beat in milk (I sometimes add a little extra milk at the end if it seems too think to spread). Add in the flour and mix until combined. Stir in Chocolate chips.
Once brownies have completely cooled spread the cookie dough on top. Place in freezer for 20-30 minutes or in refrigerator for several hours to set.
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