• Preheat oven to 350°F (180°C).
• In a food processor with the ‘S’ blade attachment, combine all the crust ingredients: almond meal, walnuts, coconut flour, egg, sweetener, and coconut oil. Process on medium speed for about 1 minute or until the mixture comes together and forms a ball.
• Transfer the dough to a bench or surface covered with a piece of food wrap. Set aside a quarter of the dough to decorate the top of the tart or to serve as biscuits with the tart on the side.
• Place another piece of cling wrap on the top of the remaining dough and start rolling the dough as you would for a regular pie crust. The cling wrap will prevent the dough from sticking to the rolling pin and the bench, so do not remove the layers until fully rolled.
• Roll to fit the size of the pie dish. Remove the top layer of cling wrap and flip the crust over onto the greased pie dish. The dough will be very crumbly but workable. If it breaks, use your fingers to shape and push the dough until it perfectly fits the dish. 
• Bake the crust for 15-20 minutes or until golden and crispy on the side. 

Blueberry chia seed jam

• To make the filling, put the chia seeds into a small bowl and add the lukewarm water. Give them a good stir and set aside for 2 minutes until they absorb the water. Give them a quick stir from time to time to stop them from sticking together.
• Meanwhile, place the blueberries and sugar-free sweetener in a saucepan, cover, and warm over medium heat. When bubbles start to form on the side of the saucepan, uncover and stir in the soaked chia seeds. Simmer for 4–8 minutes or until the blueberries are cooked, and it becomes jelly-like. 
• Pour the jam onto the prepared crust and bake for an extra 10 minutes to set.

Cookie stars decoration

• Meanwhile, prepare some pastry stars to decorate the top of the tart. If you end up with too many, they can be baked separately and served as cookies with the tart or to decorate the Christmas table.
• Roll the extra pastry dough between two pieces of cling wrap, as before, until it is the right thickness. Cut into stars using a cookie cutter. Place the stars on a baking tray covered with baking paper and bake for 10–12 minutes until golden brown
• Cool on a wire rack.  Cool completely, for about 11⁄2 hours, before you unmold the tart. This will stop the crust from falling apart as it will harden while cooling down, getting very crispy and easier to unmold.
• Store at room temperature for up to 2 days.