Place the Flour and Salt in the bowl of your food processor. Add the cold Butter cut into small cubes and blend until it forms small crumbs.

Slowly add the cold Water, a little bit at a time, blending between each addition. Stop adding water as soon as the dough comes together.

Transfer the dough over a lightly floured sheet of baking paper and bring together into a disk. Place a second sheet of baking paper over it and roll the pastry into a large rectangle. Place in the fridge to rest for at least 1 hour.

Remove the two layers of baking paper and line your baking pan with the Shortcrust Pastry. Poke small holes all over the pastry with a fork, then place back in the fridge for 30 minutes to 1 hour. Put the pastry in the freezer for the last 15 minutes before baking it.

Blind bake the pastry for 10 to 15 minutes in an oven preheated to 180?C/350?F, then set aside while you prepare the filling.

Wash the Leeks and chop into thin slices. Thinly slice the Brown Onion.

Place the Butter into a non-stick pan on medium heat. When hot, saut? the chopped Leeks, sliced Onion, and Minced Garlic for about 5 minutes until the onions are translucent. Remove from the stove.

In a separate bowl, whisk together the Eggs, Heavy Cream, Salt, Pepper, and Cumin. Add the pre-cooked Leeks and Onion, and mix in the Grated Gruyere.

Pour the filling over the pre-baked pastry and bake for another 25 to 35 minutes until the leeks are lightly golden and the filling is set. Serve warm.