Begin by creaming together the softened unsalted butter and packed brown sugar in a large mixing bowl using an electric mixer on medium speed for about 2-3 minutes until light and fluffy.

Mix in the room-temperature egg and vanilla extract until fully combined, creating a smooth base.

Gradually add the instant vanilla pudding mix, baking soda, and salt to the wet mixture, mixing until just combined.

Slowly fold in the all-purpose flour, mixing until it is just combined.

Gently fold in the pastel-colored M&Ms and sprinkles, ensuring they are evenly distributed.

Scoop tablespoon-sized balls of cookie dough onto a lined cookie sheet, cover and chill the dough in the refrigerator for at least 30 minutes.

Preheat the oven to 350°F (175°C) while the dough chills.

After chilling, place the dough balls about 2 inches apart on baking sheets and bake for 9-11 minutes or until edges are golden.

Allow the cookies to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.