Place ½ cup of unsalted butter in a saucepan and begin to melt over low heat, stirring as it melts.

Once the butter has melted, whisk in the cacao powder, powdered sweetener, vanilla extract, and salt. Continue to stir until there are no lumps.

Lower the heat to the lowest setting on the stovetop and add in the peanut butter. Continue to stir until the peanut butter has fully melted and incorporated into the mixture.

Add the chocolate chips to the saucepan keeping the heat very low. Stir continuously until the chocolate chips have fully melted and the mixture is a smooth texture. Immediately remove from heat to prevent the chocolate from getting too hot.

Transfer the mixture into a silicone mini muffin pan or a 9x9 baking pan lined with parchment paper. If using a silicone mini muffin pan, you can pour or spoon the mixture into the wells. If using a baking dish, pour the mixture and then spread it evenly using a rubber spatula. Sprinkle with flaky sea salt (if using) and place in the fridge for about 3 hours or overnight to set.

Remove the fat bombs from the molds and store them in an airtight container in the fridge for 1-2 weeks. You can allow them to thaw for several minutes at room temperature or enjoy them straight from the fridge.