Preheat oven to 350 degrees.

Place butter in a medium saucepan & cook over medium heat, stirring constantly, until melted and browned

(butter will foam & bubble as it cooks)

Once the butter is golden brown remove from the heat

Transfer browned butter to mixer bowl & let cool for several minutes

Add the brown sugar, granulated sugar, & espresso powder to the butter and beat until well combined

Beat in vanilla & eggs until just combined

Add flour, baking soda, and salt and mix until just combined

Stir in both varieties of chocolate chips slowly

Stir in 1/2 the M&M's - reserving the remaining candies for topping the cookies after baking

Portion tablespoon sized balls of dough and place on a large baking sheet

Bake for 11-12 minutes

Cookies will still be slightly underdone when you remove them from the oven. Do not overbake. Let sit on baking sheet for 5 minutes before removing to a cooling rack or eating.