In a large bowl, use an electric mixer to beat unsalted butter, creamy peanut butter, packed light brown sugar, and granulated sugar at medium-high speed until light and fluffy. This should take about 3 to 4 minutes.
Beat in eggs one at a time, stopping to scrape down sides of the bowl.
Beat in vanilla extract.
Whisk together all-purpose flour, baking powder, baking soda, salt, and ground nutmeg in a medium bowl.
Turn mixer on low and gradually add flour mixture until just combined.
Press plastic wrap down onto the dough and refrigerate for at least 2 hours and up to 3 days.
Preheat oven to 350 degrees and line 2 baking sheets with parchment paper.
Use a 1 1/2-inch spring-loaded ice cream scoop to scoop dough. Roll each dough into a uniform ball.
Place remaining 2 tablespoons of granulated sugar in a bowl. Coat the balls in sugar.
Press thumb down in the middle of each ball to make an indentation.
Bake for about 10 minutes or until just starting to turn light brown around the edges.
Let cool a few minutes and then press down on the middle of the cookies to make indentation bigger. Fill indentations with Nutella.