Preheat oven to 325 degrees F. Place store-bought crust on a baking sheet.
Melt chocolate chips in a small bowl in the microwave in 30-second intervals, stirring until smooth. Set aside to cool slightly.
Beat cream cheese and powdered sugar until completely smooth. Mix in sour cream and vanilla. Add egg and egg yolk one at a time, mixing just until incorporated. Do not overmix.
Divide the filling mixture in half. Stir melted chocolate and espresso if using into one half. Stir 1/2 cup peanut butter into the other half.
Alternate spoonfuls of chocolate and peanut butter filling into the crust. Drop the reserved 2 tablespoons of peanut butter in small dollops over the top. Use a toothpick or skewer to swirl gently.
Bake 40 to 45 minutes until edges are set and center jiggles slightly. Turn off oven, crack the door, and let cheesecake sit inside 20 minutes. Remove and cool to room temperature, then refrigerate at least 4 hours.
Make the ganache by heating heavy cream in a small saucepan over medium heat until just simmering. Pour over chocolate chips in a bowl and let sit 2 minutes, then stir until smooth. Cool 10 minutes before pouring over the chilled cheesecake.
Refrigerate 30 minutes until ganache is set. Garnish with Reese's cups or salted peanuts if desired before serving.