Begin by breaking the dark chocolate into small pieces and placing them in a microwave-safe bowl. Heat in the microwave in 30-second intervals, stirring in between, until the chocolate is completely melted and smooth. Be careful not to overheat, as chocolate can burn quickly.
Line a mini muffin tin with parchment paper or cupcake liners. This will make it easier to remove the cups once they are set.
Using a spoon or a small ladle, pour a layer of melted chocolate into each muffin cup, making sure to coat the bottom and sides evenly. You want enough chocolate to form a sturdy shell, so aim for about 1/3 of each cup filled.
Place the muffin tin in the refrigerator for about 10-15 minutes, or until the chocolate is firm to the touch.
Once the chocolate has set, remove the tin from the refrigerator. Spoon a generous dollop of smooth peanut butter into each chocolate shell, pressing down slightly to ensure it fills the cup.
Top the peanut butter layer with a spoonful of your chosen jelly or jam. Try to keep it centered within the cup to avoid overflow.
Pour a final layer of melted chocolate over the jelly, covering it completely. Use a spatula to smooth the top and ensure everything is sealed in.
Return the muffin tin to the refrigerator and allow the cups to chill for another 30 minutes, or until the chocolate is completely set.