Add flour, salt and pepper to the food processor and pulse quickly to mix. Add cold butter and pulse a few more times until there are large chunks. Add the gruyere cheese and continue to pulse until you have pea-size pieces of butter. Add half of the water and pulse a few times. Then drizzle in the remaining water and pulse until the dough just begins to come together. Don’t over-mix.

Turn the dough onto plastic wrap and gather the dough together into a disk – kneading as little as possible to get the dough to stick together. Try not to over handle the dough or it will become tough. Cover with plastic wrap and allow to rest in the fridge for 1 hour.

After 1 hour, dust the counter with flour and roll out the dough to fit your skillet size. The crust will be thick.

In a 10″ – 12″ skillet add 2 tablespoons of olive oil. *Optional: Substitute bacon grease for the olive oil for more flavor! Add the sliced leeks, season with a bit of salt and pepper and cook on medium heat for 2 – 3 minutes. Add the garlic, sage and thyme and continue to cook for an additional 3 – 5 minutes, until the leeks and garlic have softened and the herbs are fragrant.

Then add the diced parsnips and celery root and cook for 8 – 10 minutes, until the vegetables are soft. Add the butter and bullion paste and stir into the vegetables. Mix in the flour and cook for 2 – 3 minutes. Slowly add in the milk and cream stirring constantly until you have a thick gravy. Taste and adjust seasonings. Fold in the diced chicken and top with gruyere pastry crust.

Preheat the oven to 400 degrees. Cover the edges of the crust with foil to prevent burning. Bake 30 minutes, remove foil and continue to cook until the crust is golden – another 10 – 15 minutes.