Combine the ice water with the lime juice in a jug or a pitcher and set aside.
Add the cassava flour, almond flour, tapioca starch, raw cane sugar and ground chia seeds in a food processor fitted with an S blade.
Proceed to pulse (press the pulse button or use the lowest setting if you don't have one) as you slowly pour in the ice water in increments.
Once the mixture becomes crumbly (it shouldn't be too dry nor should it be too sticky, add more ice water or flour if you need to.).
Remove the mixture from the food processor and form into a pliable dough ball.
Wrap the dough ball in saran/cling film and place in the freezer for 30 minutes to chill.
Rolling the dough
After 30 minutes, unwrap the dough and lay a piece of slightly floured parchment paper on a clean surface.
Place the dough ball on the floured parchment paper then place another piece of floured parchment paper on top of the dough ball.
Use a rolling pin to roll out the dough into a rectangle (it doesn't have to be precise) about ½ -1 inch thick.
Fold the dough into thirds, as if you are folding an envelope or a letter.
Re-wrap the dough and place it in the freezer for another 30 minutes.
Making the dough
Preheat the oven at 180c/375f.
Unwrap the dough again, the place the dough on a clean surface sandwiched. between 2 lightly floured pieces of parchment paper.
Proceed to roll out the dough into a rectangle about ¼ inch thick.
Use a pizza cutter so slice the dough into 4 x 4 inch squares.
Filling the tarts
Place a few tablespoons of mango jam slightly off centre towards one half of each square (not too close to the edge, don't worry if a little jam seeps out).
Fold each square in half diagonally to create a triangle.
Use the tines of a fork to gently press around the edges of a tart to release the air then make 2-3 shallow slices on top of each tart.
Place the tarts an inch apart on a baking sheet lined with parchment paper.
Brush each tart with a "flax egg".
Bake in the oven for about 15-20 minutes or until the tarts are slightly golden with brown edges.
This is the homemade Mango Jam that you will need to make this recipe.
This recipe should make up to 10 tarts.
If you are using vegan/dairy free butter, it is a good idea to place the required amount of butter in the freezer ahead of time.
Please stick to the ingredients listed, I have tested any substitutes so if you choose to do so you are doing this at your own risk.
Keep the dough chilled at all times especially during the rolling process, if you find the dough becoming too soft even after sprinkling more flour on the parchment paper, then it is time to store the dough in the freezer.
You can refrigerate your dough but I find that the freezer gives a good blast of cool air without freezing the dough.
Store any leftover tarts in a air tight container and consume within 2 days.