1. Place rack in the middle of the oven. Preheat the oven to 190°C (375°F). Bake pie shell on middle rack for 10 minutes. Remove from oven and set aside. 
2. Meanwhile, heat oil over medium-high heat in a skillet. Add leeks and mushrooms and cook until leeks are tender, mushrooms are golden, and no liquid remains, about 8 minutes. Season with salt and pepper. 
3. Preheat the oven to 220°C (425°F).
4. In a bowl, whisk together eggs, milk, and thyme. Sprinkle ½ cup (125 mL) Swiss cheese over bottom of pie shell. Spread vegetable mixture evenly over cheese. Pour egg mixture overtop and sprinkle with remaining cheese. 
5. Bake quiche in middle of the oven for 25 minutes or until a toothpick inserted in the center comes out clean. 
6. Serve with freshly grilled asparagus from the oven.

Chef’s secret 

To avoid a soggy crust, cook vegetables until the liquid has completely evaporated.