Preheat oven to 350 degrees Fahrenheit. Line sheet trays with silicone baking mats or parchment paper. Set aside.

Cream the butter and both sugars together in the bowl of a stand mixer using the paddle attachment.

Add the peanut butter, egg, and vanilla. Mix well and scrape the bowl.

Combine the flour, baking soda, and salt. Add the dry ingredients to the wet ingredients and mix until just incorporated.

Scoop the peanut butter cookie dough into balls about 2 Tbsp each. (I use a #30 scoop.) Then roll with hands and space several inches apart onto a silicone or parchment lined baking sheet.

Bake at 350˚F for 11-12 minutes, or until just set — the tops will be puffy and matte, not shiny, when done.

Immediately after removing from oven, use the bottom of a (1/3 cup) measuring cup to flatten the center of each cookie, creating a well for the chocolate. Allow cookies to cool completely at room temperature for about 1 hour, or in the refrigerator for about 15-20 minutes. NOTE: Waiting for the cookies to cool prevents the chocolate from melting over the edges of the cookies.

Melt the chocolate chips and oil together in a microwave-safe bowl in the microwave for 20-30 second bursts. Stirring in-between each interval, until melted completely. Total time to melt chocolate will be approximately 1 minute and 30 seconds.

Spoon some of the melted chocolate into the center of each cookie. Spread evenly with the back of the spoon. Let the chocolate cool at room temperature for about 2 hours, or in the fridge for about 15-20 minutes.

Sprinkle powdered sugar over each cooled cookie and enjoy. NOTE: Waiting for the chocolate to cool prevents the powdered sugar from melting/dissolving into the chocolate.