Mix the Ingredients. Start by melting the peanut butter and butter together in a saucepan until it comes to a simmer. Remove from the heat. Stir in vanilla extract and a pinch of salt.
Combine with Powdered Sugar. Gradually add powdered sugar to the peanut butter mixture until well combined and smooth.
Set the Fudge. Spread the mixture into a lined baking dish and refrigerate until set.
Cut and Serve. Once firm, cut the fudge into squares and serve.