Line a 9x9-inch square baking pan with parchment paper or lightly grease it and set aside.

Add the butter and cream cheese to a medium saucepan and place over low heat. Cook, stirring often, until both are melted and smoothly combined.

Remove the pan from the heat and immediately add the peanut butter. Stir until the mixture is smooth and glossy with no streaks.

Add the vanilla bean paste, sugar-free powdered sweetener, whey protein powder, stevia powder, and salt to the warm peanut butter mixture.

Using an electric hand mixer, beat on low speed, then increase to medium until the mixture is thick, smooth, and fully blended with no dry patches.

If the mixture looks oily or does not blend well, let it cool for 5–10 minutes, then beat again until it comes together.

Transfer the fudge mixture to the prepared pan and spread it into an even layer with a spatula.

Refrigerate for about 2 hours, or until firm and set.

Once fully chilled, lift the fudge out of the pan using the parchment, place on a cutting board, and cut into 36 equal squares.

Store the fudge squares in an airtight container in the refrigerator until ready to serve.