Line an 8×8-inch baking pan with parchment paper, leaving a 1-inch overhang for easy fudge removal. Secure the paper with a dab of butter in each corner so it stays flat while you press in the mixture.

In a medium saucepan over low heat, melt the softened butter slowly, stirring constantly to prevent scorching and ensure an even melt. Keep the heat low—overheating can cause the dairy to separate and affect texture.

Stir in the creamy peanut butter until fully incorporated and the mixture is silky smooth, scraping down the sides of the pan to avoid clumps. If you notice any thicker bits, return it to heat for 30 seconds and stir again until completely uniform.

Remove the pan from heat, then whisk in vanilla extract and a pinch of salt to brighten the flavors. Taste a tiny bit of the mixture; the right balance of vanilla and salt will make your fudge unforgettable.

Gradually add sifted powdered sugar, one cup at a time, mixing vigorously after each addition until the dough thickens and becomes pliable. If stirring by hand feels tough, switch to a stand mixer fitted with a paddle attachment for an effortless blend.

If the mixture appears too dry or cracks when pressed, add milk one tablespoon at a time until it’s smooth yet firm enough to hold its shape. Be cautious—too much milk can prevent proper setting, so add it sparingly.

Transfer the fudge mixture to your prepared pan and press it down firmly using a flat spatula or the bottom of a glass wrapped in plastic wrap. Press until the surface is flat and edges are squared off, creating a professional look.

Refrigerate for at least 1 hour, or up to 4 hours for a firmer texture; the surface should turn matte and feel set to the touch when ready. For a quicker option, place it in the freezer for 30 to 45 minutes, just watch closely to avoid freezing solid.

Lift the fudge slab from the pan using the parchment overhang and place it on a cutting board. Cut into 36 even squares with a sharp knife dipped in hot water and wiped dry between cuts to ensure clean edges without crumbling.