Heat a frying pan over medium heat and add the butter. Let it melt, and add the leek.

Sprinkle with thyme and sauté until soft, approximately 20 minutes. Remove from heat.

Preheat oven to 350 degrees Fahrenheit (180 degrees Celsius).

Add the remaining ingredients, including the sautéed leek.

Place a malawach sheet at the bottom of a 9- or 10-inch round baking dish, if desired, or use a ready-made pie crust.

Pour the quiche ingredients over the crust or into a greased baking dish and bake, uncovered, for half an hour, or until set.