For the crust:
For the filing:
1. In a food processor process flour, salt and cold cubed butter. process until crumbs are formed. Add cold water, process until dough is formed. Do not over mix.
2. Transfer the dough to a work surface, pat into a ball and flatten into a disk. Wrap in plastic and refrigerate for 30 minutes.
3. Meanwhile make the filling: chop onions. In a large pan, melt 2 tablespoons butter and some olive oil. Add chopped onions and sauté for 5 minutes. Add crushed garlic and spinach. Cook until wilted and reduced in size. Drain.
4. In a large bowl beat eggs, heavy cream, salt, pepper and nut meg. Set aside.
5. Roll out the dough on a lightly floured board. Lightly dust the top of the dough. Roll until the dough is about 1/8 inch thick. Transfer the dough to a 9-10-inch (24-25cm) pie pan. evenly press the pastry onto the bottom and up the sides of your pan. Trim off the excess dough off the top of the pan. Gently pierce the bottom of the crust with a fork. Transfer to the freezer for 30 minutes.
6. Preheat oven to 350F (175C).
7. Blind baking: line a parchment paper over the dough. Fill with dry beans, rice or pie weights. Bake for 15 min. Remove the weights and the parchment paper. Return to oven for another 5-10 minutes or until crust is slightly golden. Remove from oven.
8. Sprinkle the spinach into the pie crust, sprinkle shredded gruyere cheese and cubed blue cheese. Pour the eggs and cream mixture over the spinach and cheese.
9. Bake until golden brown and set, about 35 minutes. Allow to cool slightly.