Make the crust: Mix the flour, potatoes and salt in a bowl and drizzle in the cold water, a tablespoon at a time, until the dough just comes together.
Wrap tightly in cling wrap, pressing with your palms as you to to shape the dough into a disc. Refrigerate while you make the filling.
Make the filling: Place the cashews in the blender along with the soaking water and blitz to get a smooth paste.
Add the chickpea flour to the blender along with salt and rosemary and 1/2 cup of water.
Blend into a smooth cream and set aside.
Heat the oil in a skillet and add the cumin and garlic. Saute for a few seconds until the garlic is fragrant but not browned.
Add the red pepper flakes and turmeric. Stir well to coat with the oil.
Add the frozen, thawed spinach, stir, cover with a lid, and cook over medium-low heat about 5-7 minutes or until the spinach is cooked.
Stir in the carrots and heat through for another two minutes.
Add salt to taste. Stir in the parsley and turn off the heat.
Let the mixture cool a little, then stir into the cashew cream-chickpea mixture.
Assemble the quiche:Preheat the oven to 350 degrees.
To make the crust, roll out the disc of dough on a clean, floured surface into a round large enough to cover the bottom and inside of an 8-inch tart pan or plate.
Fold the dough in half and transfer to the tart pan, then unfold and press into the corners with your fingers to fit it evenly into the tart pan. Cut out any overhanging dough with a knife or by rolling over the top of the pan with a rolling pin and then pulling out the extra dough with your fingers.
Place the tart pan on a baking sheet and pour the filling into the crust.
Place the baking sheet with the tart pan into the oven and bake 45 minutes or until the center is set and firm to the touch.
Remove the pan from the oven and let it cool on a rack 10-15 minutes before cutting and serving.