Add sweetener and stir with rubber spatula until the mixture browns and thickens. Once the mixture becomes sticky and golden brown, remove from heat. This should take about 7-8 minutes.
Add the peanut butter and salt once the pot is no longer on the stove. If you add the peanut butter while it is still cooking it will not turn out. Stir together until everything is smooth and incorporated.
Scoop the mixture into the wells of a silicone mini muffin pan. Place pan in freezer for at least 15 minutes or until set.
Store fudge in freezer in an airtight container. Allow to thaw for 5 minutes at room temp before enjoying.