Line a baking sheet or plate with parchment paper, set aside.
Add 1 inch of water to a medium saucepan and bring to a simmer. Place a heat-safe bowl on top of the saucepan, making sure the water is not touching the base of the bowl. Add chocolate to the bowl and melt, stirring occasionally.
In the meantime, add peanut butter and coconut oil to a microwave safe bowl and warm in the microwave until the coconut oil has melted. Stir until well incorporated.
When the chocolate is melted and perfectly smooth, transfer to prepared parchment-lined dish and smooth until it is about ¼-1/2 inch thick.
Drizzle with the peanut butter mixture. Run a knife or a toothpick through the chocolate and peanut butter in a circular motion to form decorative swirls.
Sprinkle with Reese’s Pieces and transfer to the fridge to set completely. Break into serving size pieces.