Preheat the oven to 200 °C (390 °F). Peel and finely chop 1 onion and 2 garlic cloves.
Heat a splash of olive oil in a skillet over medium heat. Sauté the onion and garlic for 3 min until translucent. Add 300 g mixed minced meat, break it up with a spoon, and fry for 6–8 min until browned and crumbly. Stir in 2 tbsp tomato paste and cook 1 min. Season with salt, pepper, a pinch of cayenne, and 1 tsp crushed oregano. Set aside.
Peel 2 carrots and 300 g celeriac; cut into small cubes. Halve 0.5 leek lengthways and slice into rings. Finely chop 1 bunch of parsley.
Add a little more oil to the pan, sauté the carrots, celeriac, and leek over medium heat for 3–4 min. Season with salt and pepper, pour in 100 ml vegetable stock, and simmer for 15 min until tender and the stock has nearly evaporated.
Combine the meat and vegetables in a bowl; stir in the parsley and 75 g grated Emmentaler. Let cool slightly.
Line an oiled 24 cm quiche pan with 0.5 package of puff pastry, pressing it up the sides. Spread the filling evenly over the base.
Whisk 2 eggs with 200 g crème fraîche and 100 ml milk; season lightly with salt and pepper. Pour over the filling and scatter the remaining 25 g Emmentaler on top.
Bake on the middle rack for 30 min, until the top is golden and the centre is just set. Serve warm or at room temperature.
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