Get Ready: Preheat your oven to a cozy 375°F (190°C). Lightly grease a baking sheet or line it with parchment paper for easy cleanup.
Mix the Wet: In a large mixing bowl, combine the natural peanut butter, brown sugar, softened unsalted butter, milk, and vanilla extract. Beat these ingredients together with an electric mixer on medium speed until they are wonderfully smooth and well blended.
Add the Egg: Gently mix in the egg until it's just incorporated into the creamy mixture. Don't overmix!
Combine Dry: In a separate bowl, whisk together the flour, baking soda, and salt. This ensures everything is evenly distributed.
Blend Together: Gradually add the dry flour mixture to your wet ingredients, mixing on low speed. Stir just until everything is combined and a soft dough forms.
Shape Your Reindeer: Roll the dough into small 1-inch balls. For that perfect reindeer shape, pinch the bottom of each ball slightly to create a point, then gently flatten it with your hand.
Bake Away: Place the shaped cookies about 2 inches apart on your prepared baking sheet. Bake for 7 to 8 minutes, or until the edges are just starting to brown and the centers are set.
Decorate Immediately: As soon as you pull the cookies from the oven, quickly (but gently!) press two mini chocolate-covered pretzels into the top of each cookie to form the antlers. Then, add two mini brown M&M's for the eyes and one red M&M for the nose. Get creative with nose colors if you like!
Cool Down: Let your adorable reindeer cookies cool on the baking sheet for about 2 minutes before carefully transferring them to a wire rack or a paper towel-lined surface to cool completely.