Preheat oven to 350 degrees Fahrenheit.
Line an 8 inch square pan with foil, letting ends extend up sides of pan.
Like so, grease and set aside.
Gather prepared ingredients.
In a large bowl, whisk egg, brown sugar, butter and vanilla until blended.
Like so, texture with be thick. *Note: mine is dark because all I had on hand was dark brown sugar.
Mix the flour with the baking soda and salt; add to brown sugar mixture.
Stir in cookies! I crunched these a little too much but it's still equally delicious 😉
Just delightful...mix together well.
Spread batter into prepared pan.
Sprinkle with M&M's!
Bake 25-30 minutes.
Cut into squares and enjoy!