• Start by chopping the chocolate into small, even pieces, or simply break it up by hand. Place the chocolate and peanut butter together in a heatproof bowl. Set the bowl over a saucepan with a small amount of gently simmering water and let everything melt slowly, stirring now and then, until the mixture is silky and well combined.
• If you prefer a quicker approach, you may melt the chocolate and peanut butter in the microwave. Heat in short 20 second bursts, stirring between each round, until smooth and fully melted.
• Once the mixture is glossy and uniform, stir in the syrup if you are using it, followed by any extras you like. Pour the warm mixture into a silicone mold, a loaf pan lined with parchment paper, or any container you have on hand. Smooth the surface with a spatula and, if desired, sprinkle a few nuts or chocolate pieces over the top.
• Place the pan in the refrigerator or freezer and let it set for one to two hours, until firm to the touch. Once set, cut into neat squares and serve.

Notes

• To adjust the texture, you can change the balance between chocolate and peanut butter. A higher amount of peanut butter will give a softer, creamier result.
• The thickness of the fudge depends on the size of the mold or pan you choose. Thinner layers will set more quickly, while thicker ones may need a bit more chilling time.