Add ½ cup of the chocolate and ½ tbsp. of the butter to a microwave safe bowl. Microwave for 15 seconds and then pull out and stir. Microwave in 15 seconds intervals, stirring every 15 seconds until the chocolate is smooth and silky. Be careful not to overcook.
Fill the bottoms of the silicon muffin liners evenly with the melted chocolate. Spread the chocolate over the entire bottom using a spoon. Place in the freezer to harden.
While chocolate hardens, combine ingredients for peanut butter filling in a mixing bowl. Make sure butter is fully softened but not melted. Using an electric hand mixer, beat until everything is incorporated and the mixture is smooth. Taste and adjust the salt and sweetener to your tastes if needed. Set aside.
Once chocolate has hardened, top with a hearty scoop of the peanut butter filing and spread. Place back in freezer.
Add 1 cup of the chocolate and 1 tbsp. of the butter to a microwave safe bowl. Microwave for 15 seconds and then pull out and stir. Microwave in 15 seconds intervals, stirring every 15 seconds like in step 3.
Spoon chocolate evenly on top of the peanut butter in each muffin liner and spread. Once all peanut butter has been topped with chocolate, pick up the muffin tin and gentle tap the bottom on the counter top several times to get the chocolate to settle evenly.
Place in the fridge for 10 minutes to harden.
Notes
Avoid melting all the chocolate at the same time because it will begin to harden in the bowl before you are able to do the top layer.