In a mixing bowl, combine the softened butter and peanut butter.
Mix until creamy using a hand mixer or whisk.
Gradually add powdered sugar to the mixture.
Continue mixing until fully combined and smooth.
Add vanilla extract and a pinch of salt, then mix well.
Line an 8x8 inch square baking dish with parchment paper.
Pour the fudge mixture into the prepared dish.
Spread evenly using a spatula.
Refrigerate for at least 2 hours until set.
Cut into squares and enjoy!