Line 10 of the cups in a standard muffin tin with paper liners. Combine the toppings you plan to use in a small bowl, mix to combine and set aside.
To melt the chocolate, heat about 2 inches of water in a small saucepan over medium heat. Place a large heatproof metal or glass bowl over the pan, making sure the bowl is dry and the water does not touch the bottom. Moisture can cause chocolate to seize. Add the chopped chocolate to the bowl and reduce the heat to low, stirring with a rubber spatula until the chocolate is smooth and fully melted. Remove the bowl from the heat.
Alternatively, place the chocolate in a glass bowl and microwave on high for 20–30 seconds. Stir, then continue heating in short intervals until the chocolate is just melted. Stir until smooth and glossy.
Spoon the melted chocolate into the lined muffin cups, filling each a little more than halfway. Sprinkle the toppings evenly over the chocolate and press lightly so they adhere. Set aside for about 2 hours, or until firm. Refrigerating or freezing the cups will speed the process. Bring to room temperature before serving.