Preheat your oven to 350°F (175°C). This ensures that your cookies bake evenly and come out perfectly chewy.
In a large mixing bowl, combine the 2 sticks of salted butter and 3/4 cup of brown sugar. Using an electric mixer, beat the mixture until it’s light and fluffy, about 2-3 minutes.
Add the 2 large eggs and 1 egg yolk to the butter mixture, along with the 2 teaspoons of vanilla extract. Mix until well combined.
In a separate bowl, whisk together the 2 1/4 cups of flour, 1 teaspoon of baking soda, and 1 teaspoon of kosher salt. Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Gently fold in the 1 1/4 cups of holiday M&Ms, 1 cup of crushed mini pretzel sticks, 1 cup of semi-sweet chocolate chips, and 1/3 cup of dark chocolate chunks until evenly distributed throughout the dough.
In a small bowl, combine 1/3 cup of granulated sugar and 2 teaspoons of cinnamon to make your cinnamon-sugar coating. Using a cookie scoop, portion out the dough and roll each piece into a ball. Roll the ball in the cinnamon-sugar mixture to coat.
Place the coated dough balls on a lined baking sheet, spacing them about 2 inches apart. Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden.
Allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a cooling rack. Enjoy your Chewy Christmas Snickerdoodles fresh out of the oven!