Lay out your mini muffin liners and place your desired filling in each one. You can use as much or as little as you'd like. The candy cups pictured are mostly chocolate but you can certainly make them mostly nuts, or fruit, etc.
Over low heat, melt the chocolate, stirring constantly. Remove the chocolate from the heat.
Gently spoon the melted chocolate into each cup. Let them set up at room temperature. You can store in the refrigerator if you'd like, but it's not required. (see note)
Notes
Like with any chocolate, make sure you store this at a consistent temperature. As long as your house isn't super warm, room temperature is totally fine! You just want to avoid repeated temperature changes because it can make the chocolate appear chalky.
Recipe by Sugar Dish Me at https://www.sugardishme.com/dark-chocolate-candy-cups/