Step 1

Line a loaf pan (8x4 inch or 5x9 inch) with waxed paper.

Step 2

In a medium saucepan over low heat, combine the peanut butter and butter. Stir until melted, then stir in the vanilla extract.

Step 3

Whisk in the sweetener and collagen until well combined and smooth. Pour the mixture into the prepared pan and refrigerate until set, about 1 hour.

Step 4

Lift the waxed paper out by the edges and cut the fudge into 15 pieces.