Preheat oven to 375°F. Line a baking sheet with parchment paper.
In the bowl of a stand mixer, beat the softened butter with both sugars on medium speed until light and fluffy (about 2–3 minutes).
Add vanilla extract and eggs, one at a time, mixing well after each addition.
Gradually mix in flour, baking soda, and salt until just combined. Do not overmix.
Fold in the M&M candies and chocolate chips using a spatula.
Scoop dough using a #40 cookie scoop (about 1.5 tablespoons per cookie).
Place dough balls on prepared baking sheet, leaving space between each cookie.
Bake for 10–11 minutes, until edges are lightly golden and centers are just set.
Let cookies cool on the baking sheet for a few minutes before transferring to a cooling rack. While cookies are warm I add the sprinkles so they do not melt while baking.
Store in an airtight container for 2–3 days or freeze up to 3 months.