1. Pre-heat oven to 400⁰F (200⁰C). Line pastry shell with foil, fill with pie weights (or dried beans) and place on a baking sheet. Bake for 15 minutes or until edges are golden. Remove from oven (leave on baking sheet), remove pie weights and let cool completely. Reduce oven temperature to 375⁰ F (190⁰C).
2. In a large skillet over medium heat, melt butter. Add leeks and mushrooms and cook, until lightly softened, about 5 minutes. Add spinach and cook, constantly stirring, until wilted, about 1 to 2 minutes.
3. Remove from heat and season with thyme, salt and pepper. Spread evenly over pastry base. Sprinkle cheese over vegetables.
4. In medium bowl, beat together eggs and cream; slowly pour over filling. Bake until filling is set in the centre, 30 to 35 minutes. Let stand for 10 minutes before cutting into wedges.
Tip: Baking the quiche on a baking sheet makes it easier to transfer the very full crust to the oven, and helps brown the bottom of the crust.
Tip: Try a different cheese, such as Jarlsberg or a white Cheddar for a different flavour combination.