In a mixing bowl, whisk together 2 ¼ cups of all-purpose flour, 1 teaspoon of baking powder, 1 teaspoon of baking soda, and ½ teaspoon of salt until well combined.

Using a stand mixer or a hand mixer, cream together ¾ cup of softened unsalted butter, ½ cup of granulated sugar, and ¾ cup of packed brown sugar on medium speed for about 1-2 minutes.

Add 1 large egg and 1 teaspoon of vanilla extract to the creamed mixture. Beat on low speed until fully blended.

Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just combined.

Gently fold in 1 ½ cups of M&Ms and, if desired, ½ cup of chocolate chips using a spatula.

Scoop the dough into 2-tablespoon portions and place them on a baking tray. Cover with plastic wrap and refrigerate for 30-60 minutes.

Preheat your oven to 350°F (175°C) while the dough chills. Line your baking sheets with parchment paper.

Bake the cookies in the preheated oven for 9-12 minutes, or until the edges are set but the centers look slightly underbaked.

Once baked, allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a wire rack.