Preheat the oven to 375°F and line two baking sheets with parchment paper or silicone mats. In a large mixing bowl, use electric beaters to cream the butter with both sugars for 1–2 minutes, until the texture is light and fluffy. Incorporate the eggs and vanilla extract, mixing until just blended.

Add the flour, baking soda, and salt, stirring until the dry ingredients are just incorporated. Gently fold in the chocolate chips and M&M’s, ensuring an even distribution throughout the dough.

Using a large cookie scoop (approximately 3 tablespoons), portion the dough onto the prepared sheets, spacing each scoop about 2 inches apart. If desired, press extra M&M’s or chocolate chips into the tops of the dough mounds.

Bake in the preheated oven for 7–10 minutes, or until the edges are lightly golden. Allow the cookies to rest on the baking sheet for 2–3 minutes before transferring to a wire rack to cool completely.