Preheat your oven to 350°F (175°C).
Line your baking sheets with parchment paper.
In a medium bowl, whisk together the all-purpose flour, baking soda, and salt.
Cream together the softened unsalted butter, brown sugar, and granulated sugar until light and fluffy, about 2-3 minutes.
Add the eggs, one at a time, mixing well after each addition, then stir in the vanilla extract.
Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined.
Gently fold in both the mini M&Ms and regular M&Ms.
Using a large cookie scoop, portion out the dough onto the prepared baking sheets.
Bake for 12-15 minutes, or until the edges are golden and the centers look slightly underbaked.
Allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a wire rack.
