Line an 8x8 inch square baking pan with parchment paper, leaving an overhang on two sides for easy removal.

In a heavy-bottomed saucepan over medium-low heat, combine the heavy whipping cream, powdered sweetener, and 2 tablespoons of the butter.

Simmer the mixture gently, stirring frequently with a heat-resistant spatula, for 40 to 45 minutes until the liquid reduces by half and achieves a thick, golden, syrupy consistency.

Remove the saucepan from the heat immediately. Add the sugar-free chocolate chips, the remaining 2 tablespoons of butter, and the sea salt to the hot mixture.

Stir vigorously until the chocolate is fully melted and the mixture is glossy and emulsified.

Stir in the vanilla extract until well incorporated.

Pour the fudge mixture into the prepared pan and smooth the top with an offset spatula.

Place the pan in the refrigerator and chill for at least 4 hours, or until the fudge is completely firm.

Using the parchment paper overhang, lift the fudge out of the pan. Slice into 32 equal squares using a sharp knife dipped in hot water and wiped dry between cuts.

Store in an airtight container in the refrigerator for up to 2 weeks or in the freezer for up to 3 months.