Wash, dry, and remove the stems from 24 grapes.
Add 1 1/2 cups chopped dark chocolate to a pot on the stove set to low heat.
Cook, stirring often, until the chocolate has melted, then immediately remove the pot from the heat.
Transfer the melted chocolate to a small bowl.
Add one grape to the bowl of melted chocolate, then gently stir to coat completely.
Use a fork to lift the chocolate coated grape out of the bowl, then place it on a large plate or sheet pan lined with parchment paper or a silicone baking mat.
Add a sprinkle of finely chopped nuts, if desired.
Repeat steps 5-7 with the rest of the grapes.
Place the plate or sheet pan of chocolate coated grapes in the fridge to harden for at least one hour before serving.