In a large bowl, use an electric mixer to beat butter, peanut butter, brown sugar, and 2/3 cup 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.
Whisk together flour, baking powder, baking soda, salt and nutmeg in a medium bowl.
Turn mixer on low and gradually add flour. Press plastic wrap down onto 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 sugar in a bowl. Coat the balls in sugar. Place on baking sheets, 2 inches apart. Press thumb down in middle of each ball to make an indentation. Sprinkle a little more sugar on tops of cookies.
Bake for about 10 minutes or until just starting to turn light brown around the edges.
Let cool a few minutes and then press bown on the middle of the cookies to make indentation bigger. Fill indentations with Nutella.