• Preheat oven to 350°F (175°C). Line two 8-inch round cake pans with parchment paper and lightly grease the sides.
• Brown the butter in a small saucepan over medium heat, stirring constantly until golden with brown specks. Remove from heat and let cool 10–15 minutes.
• In a large bowl, whisk the browned butter, dark brown sugar, and granulated sugar until smooth.
• Add eggs one at a time, whisking well after each addition. Stir in vanilla extract.
• In a separate bowl, whisk together flour, salt, and baking powder.
• Fold the dry ingredients into the wet ingredients just until combined.
• Gently fold in the chocolate chips only. Do not mix M&Ms into the dough.
• Divide the dough evenly between the prepared pans and press into an even layer. Sprinkle extra chocolate chips and M&Ms on top of each layer.
• Bake for 18–22 minutes, until edges are set and centers are just cooked through.
• Cool completely in pans, then chill layers briefly before assembling.

Frosting & Assembly

• Beat butter and cream cheese until smooth and creamy.
• Gradually add powdered sugar and salt, mixing until fluffy.
• Add vanilla, milk, and food coloring. Beat until smooth and spreadable.
• Place one cookie layer on a serving plate. Spread an even layer of frosting on top.
• Add the second cookie layer and gently press down.
• Frost the top as desired or leave sides exposed for a bakery-style look.