Melt the chocolate: Put chocolate chips in a microwave-safe bowl with 2 tbsp coconut oil and Microwave on high for 1 minute and 30 seconds then stir until smooth. (Heat longer if needed to make it shinny and melted enough to pour). (or melt chocolate in a double boiler)
Allow the chocolate to cool until it starts to get slightly thicker then fill each compartment about 1/3 way full.
Stir with a knife to coat the edges.
Spoon in about 1/2 teaspoon in the middle of each one.
Tap the ice cube tray a few times to get the peanut butter flat.
Top each one with the remaining chocolate.
Sprinkle with kosher salt if desired.
Put in freezer for about ½ hour.
Allow to warm up for about 2 minutes out of the freezer, then pop them out of the tray.
Store in the fridge or freezer.
Notes
If the chocolate is not sticking to the edges of the molds, let it cool off for a few minutes and then try again.
Don't overheat the chocolate chips. Heat just enough to melt when stirred.
If not using a microwave, use a double boiler. Do not melt chocolate chips directly in a pot.