Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a large mixing bowl, cream together the butter, granulated sugar, and brown sugar for 2-3 minutes until fluffy.

Beat in the egg and vanilla until smooth and well combined.

In a separate bowl, whisk together the flour, baking soda, and salt, then gradually incorporate into the creamed mixture.

Fold in the chocolate chips and pastel M&Ms until evenly distributed.

Scoop rounded spoonfuls of dough onto the prepared baking sheet, spacing them 2 inches apart.

Bake for approximately 12 minutes until the edges are golden brown and centers are slightly soft.

Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack.