Preheat oven to 375°F.

Stir crust ingredients together adding the water gradually until mixture sticks together. Form it into a ball. You might need to add a tablespoon or two more of water to get mixture to stick together.

Roll ball out between 2 sheets of parchment paper with a rolling pin until large enough to place into a 9 inch pie plate.

Press into the pie plate about 2/3 of the way up the sides and pinch a decorative edge into the top rim of the crust.

Bake for 10 minutes.

Add the filling ingredients to a pan and cover with lid. Cook on medium heat for about 10 minutes or until potatoes are almost soft.

Add the sauce ingredients to a blender and blend until smooth.

Mix the sauce and the potato and leek mixture together.

Pour over the crust and smooth the top.

Bake for 35 minutes.

Keep leftovers in an airtight container in the fridge for up to a week.