Preheat the oven to 350°F (175°C). Line an 8-by-8-inch (20-by-20-cm) baking pan with parchment paper.

Beat the softened butter and granulated sugar substitute together until creamy.

Add the egg and vanilla extract, then mix until smooth.

In a separate bowl, combine the almond flour, baking powder, and salt.

Add the dry ingredients to the butter mixture and stir until a thick dough forms.

Fold in the sugar-free chocolate chips and optional chopped nuts.

Press the dough evenly into the prepared baking pan and smooth the surface.

Bake for 18–24 minutes, until the edges turn lightly golden and the center looks set.

Let the bars cool in the pan for 30–45 minutes or until firm.

Lift the bars out using the parchment paper, slice into 12–16 squares, and serve.

Store in an airtight container for up to 2 days at room temperature, up to 1 week in the refrigerator, or up to 3 months in the freezer for best quality.