Prep the Oven and Pans: Preheat the oven to 350°F. Line two baking sheets with parchment paper so the cookies lift off cleanly.
Mix the Dry Ingredients: In the large mixing bowl, whisk together the flour, baking powder, baking soda, and salt until evenly combined.
1 1/2 cups plus 1 tablespoon all-purpose flour spooned and leveled, 1 teaspoon baking powder, 1/2 teaspoon baking soda, 1/4 teaspoon salt
Cream Butter and Sugars: Add the softened butter, granulated sugar, and brown sugar to the bowl. Use a hand mixer to beat for 1 to 2 minutes, until lighter in color and fluffy.
1/2 cup unsalted butter softened but still cool, 1/2 cup granulated sugar, 1/3 cup light brown sugar lightly packed
Add Egg and Vanilla: Beat in the cold egg and vanilla extract just until combined, scraping down the sides of the bowl so everything mixes evenly.
1 large egg cold, 2 teaspoons pure vanilla extract
Combine the Dough: Add the dry ingredients back in and mix on low speed just until you don’t see dry flour anymore. Don’t overmix or the cookies can turn tough.
Fold in the Mix-Ins: Use a spatula to gently stir in the M&M’s and white chocolate chips so they stay chunky and colorful.
3/4 cup Easter or spring M&M’s plus extra for topping if desired, 1/2 cup white chocolate chips or chunks plus extra for topping if desired
Scoop and Dip in Sprinkles: Pour the sprinkles into a small shallow bowl. Scoop the dough into 1 1/2 to 2 1/2 tablespoon mounds. Gently press only the tops into the sprinkles so the dough balls stay tall.
1/4 cup pastel sprinkles
Bake Until Soft-Centered: Place dough mounds on the prepared baking sheets with 1 to 2 inches of space for spreading. Bake for 8 to 11 minutes, until the edges look set but the centers still look slightly underdone.
Make Them Bakery-Pretty: While the cookies are still warm, press a few extra M&M’s and/or white chocolate chips on top if you want that “I totally planned this” look.
Cool Completely: Let cookies cool on the baking sheet for about 5 minutes, then transfer to a wire rack to cool completely and finish setting.