Mix together peanut butter, butter, and sugars in a bowl.
Roughly chop chocolate.
Melt chocolate in a heavy bottomed saucepan over low heat on the stovetop or melt in the microwave in 30-second increments, stirring in between.
Line a mini-muffin tin with paper liners or arrange the wrappers on a baking sheet.
Transfer half of the chocolate to a heatproof measuring cup with a pour spout. I used this nifty candy funnel found on Amazon (see below).
Pour just enough chocolate into each wrapper to fill the bottom about ⅛ inch.
When all of the cups are filled, gently lift and drop the tray a few times to flatten out the chocolate.
Place in the refrigerator to chill for about 10 minutes.
While the chocolate is chilling, transfer the peanut butter mixture into a piping bag or plastic bag with a small bit of the corner cut off.
Remove the chilled chocolate from the fridge.
Squeeze about a teaspoon of the peanut butter mixture in the center of each chocolate candy.
Using the tip of your finger, press the peanut butter mixture down to flatten a bit. You can press it all the way to the edge of the wrapper or leave a small space between the mixture and the wrapper that will fill with chocolate. (Moisten your finger with water so that it doesn’t stick to the peanut butter.)
Transfer the rest of the chocolate into a heatproof measuring cup with a spout or a candy funnel. (If the chocolate is not as warm/pourable as you would like, reheat it for a moment or two on the stove top, or for 10-15 seconds in the microwave).
Pour the chocolate into the cupcake wrappers until the peanut butter is just covered.
Once all are covered with chocolate, gently lift and drop the tray several times to even out the chocolate.
Sprinkle the tops with course sea salt.
Chill for 30 minutes.
Serve straight from the fridge or let them soften for 5 minutes before serving.