Heat the oven to 350°F. Line a 7x11-inch baking pan with parchment paper, leaving a little hanging over the sides so you can lift it out later.
Lay the 28 almond flour crackers in one flat layer in the pan with the edges close together.
Add the ¼ cup butter and ½ cup brown sugar Swerve to a small saucepan over low heat. Stir until the butter melts and the sweetener dissolves.
Turn the heat up to medium and bring it to a rolling boil. Boil for 3 minutes, watching so it doesn't bubble over.
Pour the hot toffee slowly over the crackers and gently spread it with an offset spatula so they're all covered and stay in place.
Bake for 10 minutes, until the toffee is bubbling across the whole pan.
As soon as it comes out, scatter the ½ cup chocolate chips over the top. Wait 2 to 3 minutes, then spread the melted chocolate into an even layer.
Sprinkle the ¼ cup chopped pecans over the chocolate, if using, and press them in lightly.
Refrigerate for 2 hours, until the chocolate is firm. Lift it out with the parchment and break it into about 24 pieces.