Line a baking sheet with parchment paper or a silicone baking mat and set aside. Measure out the 8 ounces finely chopped dark chocolate, 6 ounces peanut butter chips, and 1 cup mini peanut butter cups.

Melt the dark chocolate: place the 8 ounces of finely chopped chocolate in a heatproof bowl. Use one of these methods: - Double boiler: set the bowl over (not touching) gently simmering water and stir frequently until the chocolate is just melted and smooth. Remove the bowl from the heat and continue stirring off the heat until fully smooth. Avoid letting steam or water contact the chocolate. - Microwave: microwave on medium power in 15–20 second intervals, stirring well between each interval, until the chocolate is smooth and fully melted. Do not overheat.

Melt the peanut butter chips: place the 6 ounces of peanut butter chips in a microwave-safe bowl. Microwave on medium power in 20-second intervals, stirring between each interval, until the chips are smooth and “drizzleable.”

If the melted peanut butter chips are too thick to drizzle, add up to the 1 tablespoon of unflavored vegetable shortening or coconut oil from the ingredient list. Add a small amount at a time and stir until the peanut butter chips reach a drizzleable consistency.

Pour the melted dark chocolate onto the prepared baking sheet. Use an offset spatula or the back of a spoon to spread it into an even layer to the thickness you want for the finished bark.

Drizzle the melted peanut butter chips over the chocolate in lines or blobs. Use a toothpick or skewer to drag through the two layers to create decorative swirls.

Evenly scatter the 1 cup mini peanut butter cups over the top of the swirled chocolate, pressing each cup gently into the chocolate so it sticks.

Let the bark set, uncovered at room temperature, until firm, about 1 to 2 hours. Once set, break or cut into serving-size pieces.