You will need a roughly 8 inch round pie or tart pan.
Preheat the oven to 350°F (180°C or 170° for a fan oven).
Remove the ready rolled pastry from the fridge according to package directions or make homemade shortcrust pastry.
Heat the oil in a frying pan over medium heat.
Sauté the leeks for three to four minutes, stirring constantly, until they are nicely softened.
Remove from the heat and set aside to cool a bit.
In a medium bowl or pitcher, beat together the eggs and milk.
Beat the basil, oregano, garlic salt and freshly ground pepper into the egg and milk mixture.
Put a baking sheet into the oven to preheat.
Roll out the pastry or unroll the ready rolled pastry carefully.
Line your pie plate or tart pan with the pastry.
Trim the edges of your pastry and prick the base several times with a fork.
Scatter the (slightly cooled) leeks and sliced sausages over the bottom of the pastry base.
Gently pour the egg, milk and herb mixture over top.
Place the pie plate or tart pan in the oven on top of the baking sheet.
Bake for 25 to 30 minutes or until the quiche filling is set and is beginning to take on a golden colour.