Grease a 9 x 13-inch baking pan with butter or cooking spray.

In a mixing bowl, beat together butter and sugars with an electric mixer on medium speed until light and fluffy, two to three minutes. Add vanilla and milk. Mix in flour and salt and beat on low speed (or by hand) until incorporated. Stir in chocolate chips.

Melt butter and marshmallows together in a large saucepan over low heat, stirring occasionally, until completely melted. Remove from heat and add vanilla. Fold in cereal, gently stirring until completely coated.

Press half of the cereal mixture into prepared pan. Spread with cookie dough and then top with remaining cereal, carefully pressing into an even layer. (You may find it easier to use your hands for this step; if so, generously butter them beforehand so the cereal mixture doesn’t stick to your fingers). Cut into squares.