Melt the dark chocolate chips and coconut oil together until smooth.
Line a muffin tin with paper liners. Spoon a small amount of melted chocolate into each liner and spread evenly.
Place in the freezer for 10 minutes to set.
In a mixing bowl, combine peanut butter, maple syrup, vanilla extract, and sea salt.
Spoon a small amount of the peanut butter mixture over the set chocolate layers.
Pour the remaining melted chocolate over the peanut butter layer, covering completely.
Chill in the freezer for 20 minutes until fully set.
Enjoy immediately or store in the refrigerator for up to a week.
Notes
For a nut-free version, substitute peanut butter with sunflower seed butter. These peanut butter cups are best stored in the fridge to keep their shape.