Get Ready: Preheat your oven to 350°F (175°C).
Make the Base: In a medium bowl, combine the almond flour, the first measure of sugar-free sweetener, salt, softened butter, and the first measure of vanilla extract. Mix until it forms a uniform dough. Press this mixture evenly into the bottom of an 8x8 inch square baking dish.
Bake the Crust: Place the dish in the preheated oven and bake for 15-20 minutes, or until the edges are lightly golden brown.
Prepare Peanut Butter: While the crust is baking, whisk together the peanut butter, the second measure of sugar-free sweetener, and the second measure of vanilla extract in the same bowl you used for the crust (no need to wash!). If your peanut butter is stiff, microwave it for about 30 seconds to make it easier to spread.
Layer it Up: Once the shortbread crust is out of the oven, drop small dollops of the peanut butter mixture evenly over the warm crust. Allow it to sit for a few minutes so the warmth helps soften the peanut butter, then gently spread it with a spatula to cover the crust completely. Be gentle to avoid crumbling the base.
Add Chocolate Finish: Melt the chopped dark chocolate in the microwave (stirring every 30 seconds) or over a double boiler until smooth. Pour the melted chocolate over the peanut butter layer, then gently spread it out.
Chill & Enjoy: Transfer the baking dish to the refrigerator and chill until the chocolate layer is completely firm, about 30 minutes. Once firm, cut the bars into 16 squares and enjoy your wholesome, homemade treat!