Line an 8x8-inch pan with parchment paper, leaving some overhang for easy lifting. Lightly grease the parchment.

In a microwave-safe bowl, combine butter and unsweetened chocolate. Heat in 20–30 second bursts, stirring between each, until smooth. Alternatively, melt gently on the stovetop using a double boiler.

Whisk in the almond butter until the mixture is glossy and fully combined. If using peanut butter, make sure it’s the no-sugar-added kind.

Stir in the heavy cream, powdered sweetener, vanilla, and salt. Mix well until silky. If the sweetener clumps, keep whisking or use an immersion blender for a few seconds.

Taste and adjust sweetness. Allulose tends to taste smoother and less cooling; erythritol blends may need a touch more cream to avoid grittiness.

Fold in any optional add-ins, like chopped nuts or coconut. Don’t overmix or the nuts can sink.

Pour the mixture into the prepared pan and smooth the top with a spatula. Tap the pan lightly to release air bubbles.

Refrigerate for 2–3 hours, or until firm enough to slice. For faster setting, chill in the freezer for 45–60 minutes.

Lift the fudge out using the parchment and cut into small squares. A hot knife (run under warm water and dried) makes clean cuts.

Serve chilled or slightly cool. Store leftovers in an airtight container in the fridge.