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

In a medium mixing bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt until well-blended. Set aside.

In a separate large bowl, cream together the softened butter, granulated sugar, and packed brown sugar using an electric mixer on medium speed until light and fluffy, about 2-3 minutes.

Mix in the lightly beaten egg and vanilla extract into the butter-sugar mixture until fully incorporated.

Gradually add the dry flour mixture to the wet ingredients, mixing gently until just combined.

Using a cookie scoop or two tablespoons, portion out the dough into balls about 2-3 tablespoons each and place them on the prepared baking sheet, spacing them 2-3 inches apart.

Bake for 10-12 minutes, until the edges are lightly golden and the centers remain soft and puffy.

Press nine pastel M&Ms into the center of each warm cookie, then allow to cool on the baking sheet for a few minutes before transferring to a wire rack.