Step 1: Make the Pastry

1. In a mixing bowl, rub the butter into the flour using your fingertips until the mixture resembles breadcrumbs.
2. Add the egg yolk and 2 tablespoons of cold water. Mix until the dough comes together. Add a little more water if necessary.
3. Wrap the dough in cling film and chill in the fridge for 30 minutes.

Step 2: Prepare the Pastry Shell

1. Preheat the oven to 200°C (180°C fan) or 400°F.
2. Roll out the chilled pastry on a floured surface and line the tart tin. Trim any excess pastry.
3. Prick the base with a fork and line with baking parchment. Fill with baking beans or dried rice.
4. Blind bake the pastry for 15 minutes. Remove the beans and parchment, then bake for another 5 minutes to crisp up the base.

Step 3: Cook the Bacon

In a skillet over medium heat, cook the bacon lardons until golden and crisp. Drain on paper towels and set aside.

Step 4: Make the Filling

1. In a bowl, whisk together the eggs, double cream, milk, salt, and pepper until smooth.
2. Stir in the grated Gruyère cheese and cooked bacon lardons.

Step 5: Assemble the Quiche

Pour the filling into the baked pastry shell, spreading it evenly.

Step 6: Bake the Quiche

Reduce the oven temperature to 180°C (160°C fan) or 350°F. Bake the quiche for 25-30 minutes, or until the filling is set and golden brown.

Step 7: Cool and Serve

Let the quiche cool slightly before slicing. Serve warm or at room temperature.