To prepare the pastry, add the ground almonds to a food processor along with the flax, butter, 1 tablespoon of erythritol, cinnamon and salt. Blend to form a chunky crumb.
Add the egg to the food processor and blend again until a dough forms.
Remove the dough and cover with plastic wrap. Refrigerate for 15 minutes.
Whilst the dough is chilling you can prepare the filling. Add 2 tablespoons of almond butter to a mixing bowl with the cocoa powder and 1 tablespoon of lakanto syrup. Stir together until well combined.
Remove the dough from the fridge and open out on the plastic wrap. Lay another sheet of plastic wrap over the top and roll the dough into a rectangle about 4mm thick. Score the dough into 8 even rectangles.
Preheat the oven to 350 degrees Fahrenheit and line a shallow oven tray with baking paper.
Divide the filling mixture evenly between four of the pastry rectangles, leaving a gap all the way around the edges.
Flip the uncovered pastry over onto the chocolate covered pastry forming a lid.
Pinch the sides of the dough together with your hands to seal it shut, then use a fork to crimp around the edges.
Transfer the pastries to the lined oven tray to bake for 5 minutes, carefully turn each pastry over and bake for a further 4-5 minutes until the edges are golden brown. Remove and set aside to cool.
Whilst the pastry is cooking you can prepare the glaze. Add the almond milk, 1/2 tablespoon of almond butter, 1 tablespoon of erythritol and 1 tablespoon of lakanto syrup to a small pan. Bring the mixture to a rapid boil over a high heat, stirring well to combine and dissolve the almond butter. Reduce the heat and stir in the chocolate chips. Stir continuously for a minute or two until you have a thick, reduced toffee like consistency.
Liberally coat each pastry with the glaze before serving.