Preheat the oven to 350 degrees F. Line a cookie sheet with parchment paper and set aside.
In a medium bowl, whisk together flour, baking soda and salt and set aside.
2 1/4 cups all purpose flour, 1 teaspoon baking soda, 1/2 teaspoon salt
In a separate bowl with a hand mixer, or in the bowl of a stand mixer fitted with the paddle attachment, cream the butter, brown sugar, and white sugar on high speed until light and creamy, at least 3 minutes. Do not skip this step.
1 cup unsalted butter, 3/4 cup light brown sugar, 1/4 cup granulated sugar
Add the dry pudding mix, vanilla and eggs and beat on high for 2-3 minutes, until light and fluffy.
3.4 ounces vanilla instant pudding mix, 2 large eggs, 1 teaspoon vanilla extract
Slowly add half of the dry ingredients to the wet ingredients and turn the mixer on low speed to start so the flour doesn't get everywhere. Turn the mixer up to high speed and mix until combined. Add the rest of the dry ingredients and repeat until dough is just combined. Stir in the M&Ms with a rubber spatula until incorporated.
1 1/2 cups M&Ms
Use a large cookie scoop or 1/4 cup measuring cup to drop the cookie dough balls onto the prepared baking sheet. Bake for 10-12 minutes, or until slightly golden and just set on the top. Allow to cool on the baking sheet for two minutes. Press extra M&Ms into the tops while they cool. Transfer them to a wire rack to cool completely.