Prep the pan: Line an 8x8-inch baking pan with parchment, leaving overhang for easy lifting. Lightly grease the parchment if you like.

Toast the walnuts: In a dry skillet over medium heat, toast chopped walnuts for 3–5 minutes, stirring often, until fragrant. Set aside to cool.

Soften the base: In a medium saucepan over low heat, add butter and cream cheese (both cut into chunks). Stir continuously until mostly melted and smooth. Keep the heat low to avoid scorching.

Add sweetener and flavor: Whisk in powdered sweetener, a pinch of sea salt, and vanilla. If using heavy cream, add 1–2 tablespoons now for extra creaminess.

Maple time: Stir in keto maple syrup for deeper flavor and a slightly chewier set, or add 1–2 teaspoons maple extract if you prefer lower carbs and a firmer set. Taste and adjust sweetness or maple intensity.

Smooth it out: Continue whisking over low heat until the mixture is glossy and uniform, about 2–3 minutes. Avoid boiling. If adding a pinch of cinnamon or nutmeg, whisk it in now.

Fold in walnuts: Remove from heat and stir in most of the toasted walnuts, reserving a small handful for the top.

Pour and level: Transfer mixture to the prepared pan. Spread evenly with a spatula and tap the pan gently on the counter to release air bubbles.

Top and chill: Sprinkle remaining walnuts over the top and lightly press them in. Refrigerate for at least 2–3 hours, or until fully set and firm to the touch.

Slice and serve: Lift the fudge out with the parchment. Cut into small squares (25–36 pieces). Keep chilled until serving for best texture.