Creating the Holiday Chunky M&M Cookie is simple when you follow these easy steps:

1. Preheat Oven: Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
2. Cream Butter and Sugars: In a large mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.
3. Add Egg and Vanilla: Beat in the egg and vanilla extract until fully combined.
4. Combine Dry Ingredients: In another bowl, whisk together the flour, baking soda, and salt.
5. Mix Dry and Wet Ingredients: Gradually add the dry ingredients to the wet mixture, mixing until just combined. Do not overmix.
6. Fold in M&Ms: Gently fold in the chunky M&Ms and chocolate chips if using, ensuring they are evenly distributed throughout the dough.
7. Scoop Dough: Using a cookie scoop or tablespoon, drop rounded balls of dough onto the prepared baking sheet, spacing them about 2 inches apart.
8. Bake: Place the baking sheet in the preheated oven and bake for 10-12 minutes or until the edges are golden brown and the centers are slightly soft.
9. Cool: Remove from the oven and let the cookies cool on the baking sheet for 5-10 minutes before transferring them to a wire rack to cool completely.

These steps will guide you in creating the incredible Holiday Chunky M&M Cookie effortlessly!