Preheat oven to 350°F. Line a large baking sheet with parchment paper.
In a large bowl, mix the peanut butter, brown sugar, granulated sugar, egg, and vanilla extract until smooth and well combined.
Add the flour, salt, and baking powder to the wet mixture. Stir until a dough forms. If the dough feels too dry or crumbly, add the tablespoon of water or milk and mix again.
Use a 2 tablespoons cookie scoop to portion the dough into evenly sized balls and place on baking sheet 2 inches apart.
Use your thumb or the back of a teaspoon measuring spoon to press a small indent into the center of each ball, forming a "well."
Bake the cookies for 10-12 minutes or until the edges are slightly golden.
Remove the cookies from the oven and let them cool on the baking sheet.
While the cookies are cooling, melt the chocolate chips in the microwave or using a double boiler.If using a microwave, place the chocolate chips in a microwave safe bowl and heat in 30 second intervals at 50% power, stirring well between each interval, until chocolate is melted and smooth.Stir in the peanut butter until the mixture is smooth and fully combined. Spoon 1-2 teaspoons of the chocolate-peanut butter mixture into the "well" of each cookie.
Sprinkle finely chopped peanuts over the filling before it sets to add a crunchy texture and enhance the peanut flavor.
Allow the filling to set before serving.