Start by making the filling.
Heat up the oil in a pan, chop the leek and mushrooms, and sautee until tender and all the liquid is released, that should take about 10-15 minutes.
Season with salt and pepper, and set aside.
To make the crust, cut the cold butter into cubes, add it to the flour, and use your fingers to rub the butter with the flour until it resembles breadcrumbs.
Add the cold water, and bring together into a dough.
Refrigerate it for at least 30 minutes.
Transfer the dough to the work surface, and use a rolling pin to roll in into about ¼ cm thickness.
Spread it over a quiche/tart dish, making sure the edges of the dish are covered by dough too, not just the bottom.
Cover the crust with kitchen foil, then fill it with any pulses you have around: lentils, rice, etc If you have baking ceramic balls, even better.
Bake in the pre-heated oven at 180 degrees Celsius (360 Fahrenheit) for 15 minutes, then remove the foil and pulses, and bake for a further 5 minutes until cooked through.
Beat the eggs with a pinch of salt, add the milk and cream and whisk well to combine.
Arrange the mushroom and leek filling, pour over the egg mixture, and top with the asparagus tips.
Bake for a further 20 minutes or until the filling is set and golden.