Preheat oven to 425 degrees F.
Add the crust ingredients to a Thermomix® mixing bowl or stand mixer and knead/mix for 3 minutes.
Press the dough into a quiche dish, poke holes in the dough with a fork, and bake in the oven for 15 minutes.
In the meantime, heat the olive oil in a skillet over medium heat and cook the leek and mushrooms, mixing occasionally, for 7 minutes.
Add the eggs, half-and-half/milk, salt, pepper and nutmeg to a mixing bowl and whisk together until blended.
Add half of the cheese and mix well.
Place the vegetables on the quiche crust, then pour the egg mixture on top.
Sprinkle remaining cheese on top.
Bake at 425 F for 15 minutes, then lower the heat to 325 degrees F and bake for 30 minutes or until top is golden brown.