Preheat the oven to 350°F / 175°C. Line a baking sheet with parchment paper or a silicone baking mat.
Add the butter to a small mixing bowl that is microwave safe and microwave it until it's fully melted. Immediately whisk in the peanut butter until it's completely melted and the mixture is smooth.
Add in the brown sugar, egg yolk, milk and vanilla. Whisk until well combined.
Add in the flour, baking soda, baking powder and salt. Fold the mixture together just until no more flour streaks remain.
Make the coating by mixing the sugar and nutmeg together in a small bowl.
Use a 1.5 tbsp. cookie scoop to dish out the dough, then roll each cookie in the nutmeg sugar.
Evenly space out the coated scoops of the cookie dough on the cookie sheet and bake for 8 minutes. While the cookies are baking, unwrap 10 hershey's kisses so that they are ready when the cookies come out of the oven.
IMMEDIATELY after the cookies come out of the oven, press a kiss into the center of each one. Once all the cookies have a kiss, place them in the fridge to chill for 10-15 minutes or until the cookies are no longer warm.
Serve and enjoy!