Separate paper muffin liners and set them aside.
Melt the chocolate by mixing the chips and oil in a basin that may be heated in the microwave. Stir occasionally and cook for 30 seconds at a time in the microwave until melted and smooth.
Place a spoonful of melted chocolate into the base of each paper liner to create the bottom layer. Make a cup shape with the chocolate by gently drawing it up the sides with the back of the spoon. Freeze for ten minutes.
In a separate dish, pour the peanut butter, powdered sugar, and vanilla extract and stir until smooth to make the filling.
Take the baking sheet out of the freezer. Make a little space in the bottom of each chocolate cup and spoon a little peanut butter mixture on top.
If the leftover chocolate has solidified, re-melt it before sealing the cups. Spread it out evenly over the peanut butter filling. Lightly tap the tray on the counter to eliminate any air bubbles and level the surface.
Add a pinch of sea salt to each cup for an added burst of flavor.
Return to the freezer and continue freezing for another 15 to 20 minutes.
When the peanut butter cups are solid, take them out of the paper liners. They are best enjoyed right away, although they keep well in the fridge if sealed.
