Prepare the shortcrust pastry. In a large mixing bowl, add the flour and salt, forming a well in the center. Place the softened, diced butter into the well. Using your fingertips, gently work the butter into the flour, gradually incorporating 4 to 5 tablespoons of cold water. Mix until the dough comes together into a ball. Knead lightly until the dough is smooth and no longer sticky.
Preheat the oven to 400°F (200°C).
In a skillet over medium heat, cook the lardons (or diced bacon) until golden and crispy. Drain on a paper towel to remove excess fat.
On a floured surface, roll the dough into a circle about 1/8 inch (3 mm) thick. Carefully place it into a round tart pan, pressing the edges to form a neat border. Prick the base of the pastry with a fork to prevent it from puffing up during baking.
Evenly distribute the cooked lardons over the pastry base.
In a separate bowl, whisk the eggs and crème fraîche together until smooth. Season with a little salt (keeping in mind the lardons are already salty), freshly ground black pepper, and a pinch of ground nutmeg.
Pour the mixture over the lardons in the tart shell. Bake for 10 minutes at 400°F (200°C), then reduce the temperature to 350°F (180°C) and bake for an additional 20–25 minutes, or until the filling is set and golden.
Let the quiche cool for about 5 minutes before removing it from the pan. Serve warm, accompanied by a green salad. Typically, one-quarter of the quiche served with salad is sufficient per person.