Pre-heat the oven to 400°F (200°C).
In a food processor, mix the flour and salt. Add the duck fat. Mix for a few seconds at a time until fat pieces are the size of peas. Add water. Mix until the dough just starts to form in the processor bowl. Add water only as needed to form a non-sticky ball. Remove the dough from the food processor. Form two thick patties and place in two Ziploc bags. Refrigerate for 1 hour.
Boil the potato, skin on, then peel and mash with a fork to obtain a relatively smooth texture.
Debone the duck. Set aside only the deboned thighs with skin (approx. 335 g) and the deboned breasts and filets with skin (approx. 450 g). Cut into pieces. Place the very cold meat in a meat grinder, and using the coarse setting attachment, coarsely grind meat.
In a large saucepan, cook the onion and garlic in the hot duck fat. Add the meat, thyme and five spice. Cook over low heat for 5 minutes, stirring occasionally. Season with salt and pepper, and mix thoroughly. Add the stock and cook over low heat for about 25 minutes or until fully cooked, stirring from time to time. Remove from heat and combine the meat with the mashed potato and maple syrup. Correct seasoning as needed. Let cool.
Take the dough out of the refrigerator and flatten to a thickness of approx. 4 mm between two pieces of parchment paper. Place one piece of rolled out dough in a 9-inch Pyrex pie dish, and pour filling on top. Cover with the other piece of rolled out dough. Make three incisions in the centre. Seal the edges with a bit of water. Brush the tourtière with the egg yolk, and dust with maple fleur de sel.
Bake in the oven at 400 °F (200°C) on the lower rack for approximately 30 minutes. Reduce the oven temperature to 350 °F (175°C) and cook until the tourtière is golden brown, approx. 40 minutes. In the last 5 minutes of cooking, lightly brush the crust with 1 tsp. of maple syrup. Remove from the oven and let stand for 30 minutes before serving.
Serve with fruit ketchup. A pure delight!
Recipe from Domenico Forte, professional chef