Place 1 cup of creamy peanut butter and 1 cup of unsalted butter in a microwave-safe bowl. Microwave on high for about 2 minutes, then stir to help melt the fats evenly.
If the mixture is not fully melted, microwave for another 1-2 minutes until smooth. Stir in 1 teaspoon of non-alcoholic vanilla extract until fully incorporated.
Gradually add 4 cups of powdered sugar while stirring continuously. The mixture will thicken and become stiff, ensuring the fudge sets properly.
Transfer the thick fudge mixture into an 8x8-inch dish lined with parchment paper, pressing it firmly and evenly with a silicone spatula.
Refrigerate for at least 2 hours until completely firm.
Once set, lift the fudge out using the parchment paper and cut into small squares.
