In a small mixing bowl, beat egg and buttermilk together and set aside.
In a seperate (and significantly larger) bowl, add arrowroot, buckwheat flour, coconut flour and salt and whisk until well incorporated. Whisk in almond meal, blend thoroughly and make a well in the middle.
Pour egg mixture into the well and progressively mix in flour mixture with your fingers or wooden spatula. Continue mixing until dough comes together then turn over onto a floured surface (make sure to use grain free flour!)
Knead dough for about a minute, until really well incorporated then shape into a flat rectangle. Cover with plastic film and refrigerate for at least 30 minutes.
The easiest way to roll this dough is between two sheets of parchement paper, but you could also choose to do it on a floured surface. Again, make sure to use non grain flour, such as quinoa. Roll the dough to form a square large enough to cover large individual quiche dishes.
Now this dough doesn’t have any gluten to hold it together, so you might not be able to lift it and place it onto your dishes in one piece. Get ready to do a little bit of patchwork!
Cut your dough into 4 pieces and place each piece onto an individual quiche dish. If your dough should rip or even break, which will probably happen, don't worry about it. Just stitch and repair the pieces as you go, until your dish is entirely covered, sides and all.
Repeat with remaining 3 pieces and set aside.
For the filling
Set your oven to broil
Line a baking sheet with parchement paper and set aside.
In a large mixing bowl, add sweet potato, apple, olive oil, salt and pepper. Toss to coat evenly and transfer onto reserved pan.
Place in oven under broiler and cook until potato and apple start to caramelize and turn slightly golden.
Remove from oven and set temperature to 375F
Transfer potato mixture back to large mixing bowl and add the rest of the ingredients.
Mix well and divide between the 4 reserved pie shells.
Place in the oven and cook for about 40 minutes, or until nice and golden brown.