Preheat the oven to 350 degrees.

Line a baking sheet with parchment. Set aside.

In a medium mixing bowl, combine the melted butter and the brown sugar. Whisk until smooth.

Stir in the egg yolk.

Work in the dry ingredients - four, baking soda, and table salt. If you are doing this by hand, it will be firm - just keep working until all of the flour is incorporated.

Fold in the chocolate chips and the M&M’s.

Divide the dough into 6-8 equal portions - 6 cookies are quite large, 8 cookies bake to a standard-sized cookie.

Sprinkle with a pinch of the flaky sea salt.

Place on the prepared baking sheet and bake for 8-10 minutes or until the tops are just set.

Once the cookies are done baking, add a few more M&M’s and flaky sea salt to the tops for added visual interest and flavor.

Let the cookies cool for a few minutes on the baking sheet before transferring to a wire rack to cool completely before storing.

These cookies can be stored in a small airtight container at room temperature for several days. But they are usually gone long before then.