Preheat oven to 350F. Render bacon over medium heat, then turn the heat to medium-high. Add oil. Add mushroom, leeks and garlic; sauté until vegetables are cooked through and mixture is fairly dry. Divide mixture between the 36 tart shells and top each with equal amounts of mozzarella. Don't press the mixture in. Leave it fairly loose so that the egg mixture can fill in all the spaces. In a bowl, beat together eggs, cream and seasonings. Divide the egg mixture between all the filled tart shells. Tap the pan on the counter to be sure there are no air pockets. Top up with more egg mixture if needed. Bake on a cookie sheet for about 15 minutes. The quiches should be a little brown on top, the filling slightly puffed and the crust brown. Yield: 36.