Bake 11–12 minutes, until centers are set but still soft.
Let cookies cool completely on the sheet.
Prepare the Peanut Butter Filling
In a clean bowl, beat ½ cup butter and peanut butter until smooth.
Add powdered sugar and vanilla. Mix on low, then medium, until thick like frosting.
Make the Ganache
In a microwave-safe bowl, combine chocolate chips and cream.
Microwave 1 minute, stir; heat another 15–30 seconds if needed.
Stir until glossy and smooth. Let cool to room temperature.
Assemble the Cookies
Spread a thin layer of peanut butter filling on each cookie.
Top with a spoonful of ganache and smooth it out.
Let sit at room temperature until the ganache sets.
Notes
Double-Chocolate Buckeyes: Fold ½ cup mini chocolate chips into the dough for extra melty pockets in every bite.Storage: Store your Buckeye brownie cookies in an airtight container at room temperature for up to 3 days, or refrigerate for up to 7 days. Layer with parchment paper to keep the peanut butter filling and ganache from sticking.