1. Combine the flour and salt for the dough in a bowl. Add the cold butter (cut into small pieces) and use a pastry blender* to cut it into even smaller pea-sized pieces. Next, add the ice water and work everything into a smooth dough. If the dough doesn’t hold together, add a little more water and work it in. Wrap the dough in plastic wrap and place it in the fridge for about 1 hour.

2. Lightly grease a 24cm tart tin with a removable bottom* and set it aside. Roll out the dough on a lightly floured surface until it is slightly larger than the tart tin, then place it in the tin and press firmly against the bottom and sides. Trim off any excess dough overlapping the edges. Prick the base several times with a fork and place in the refrigerator until ready to use.

3. Finely dice the bacon for the filling. Peel and finely dice the onions. Finely grate the Gruyère cheese. Set everything aside.

4. Heat a little olive oil in a frying pan, add the diced bacon, and fry until it has taken on some color. Remove it from the frying pan and set aside in a bowl. Add a little more oil to the frying pan, heat it up, then add the diced onions and sauté them for a few minutes until softened and slightly browned. Deglaze the onions with the apple cider and let it cook down until almost completely gone. Add the onions to the fried bacon and mix well.

5. Preheat the oven to 200°C (390°F). Mix the sour cream well with the eggs. Add about 3.5 oz./100g of the grated cheese and mix it in. Season everything well with salt, pepper, and some freshly grated nutmeg.

6. Remove the prepared tart tin from the fridge and place it on a baking sheet. Spread the bacon and onion mixture evenly inside the crust, then pour the sour cream, egg, and cheese mixture on top. Ensure everything is distributed evenly. Sprinkle the remaining cheese on top and bake the quiche in the preheated oven for about 32–35 minutes. The filling should have set and nicely browned. If you think the filling gets too dark towards the end of the baking time, simply slide a baking sheet onto the rack above it to shield the quiche from some of the heat. Remove the finished quiche from the oven, let it cool on a wire rack for about 15–20 minutes, and then serve it (luke)warm or cold.