For the Cookies

1. Preheat the oven to 350° F. Line a large cookie sheet with a silicone baking mat or parchment paper.
2. Combine the softened butter with peanut butter and beat until completely smooth; scrape down the bowl occasionally. Next add the brown and white sugar and beat until well combined.
3. Add the vanilla, egg, baking soda and salt and mix until smooth. Then add the flour and mix just until the dough forms.
4. Place the chopped peanuts in a small bowl. Use a medium-sized cookie scoop to portion out the dough into balls, then roll each one smooth between your hands. Roll each ball in the peanuts, pressing lightly to adhere. Place on the prepared cookie sheet.
5. Bake for 9 to 11 minutes, rotating the pan halfway through baking just until they have a glossy sheen and the bottoms have started to brown. These will not spread during baking
6. Remove from the oven and use a teaspoon to press into the center of the cookie to create a cavity. Allow them to cool on the cookie sheet before transferring to a wire rack to cool completely.

For the Filling

1. Once the cookies have cooled, make the ganache. In a microwave-proof bowl, combine the chocolate chips and heavy cream. Microwave in 30-second increments, stirring frequently until the chocolate is melted and smooth.
2. Spoon the ganache into the center of each cookie. The ganache will harden as it cools.