Start by lining your silicone molds or cupcake liners on a baking sheet for easier transfer to the fridge or freezer.
In a microwave-safe bowl, add the chocolate chips and optional vegetable or coconut oil. Microwave in 30-second intervals, stirring between, until fully melted and smooth.
Spoon a small amount of melted chocolate into each mold, spreading evenly to cover the bottom. Refrigerate for about 10 minutes to set.
In a separate bowl, mix peanut butter, sweetener (if using), and a pinch of salt until well combined to create a creamy filling.
Remove molds from the fridge and spoon the peanut butter mixture on top of the chocolate base, filling each mold almost to the top.
Pour the remaining melted chocolate over the peanut butter filling, covering it completely and smoothing the top with a spatula if needed.
Return the molds to the refrigerator for 20-30 minutes or freezer for 10-15 minutes until chocolate is fully set.
Carefully remove the peanut butter cups from molds or peel away cupcake liners. Enjoy!