Roughly chop the unsweetened chocolate for the chocolate shell.
Place the chocolate chunks in a microwave-safe bowl, and microwave on high for 1-2 minutes, stirring every 15 seconds.
Once melted, remove from microwave and mix in protein powder, butter, and erythritol-stevia blend.
Pour half of the chocolate mixture into small silicone molds, filling up each only about halfway.
Note: If you do not have a silicone mold, you can use cupcake tins to achieve a similar shape.
Place the chocolate shells into the freezer to harden.
In a microwave-safe bowl melt together remaining peanut butter and butter for 1 minute, stirring every 15 seconds.
Stir in the remaining sweeteners and spices.
Remove the chocolate shells from the freezer.
Top each previously hardened chocolate mold evenly with peanut butter mixture, place in the refrigerator to harden, then top evenly with remaining chocolate.
For a more solid texture, store your keto Reese's Cup fat bombs in the fridge in an air-tight container.