Preheat oven to 375°F. Whisk together eggs, cream, celery salt and pepper. Set aside.
Heat olive oil over medium-high heat in a large frying pan. Sauté mushrooms and leeks until the leeks have softened, about 2 minutes. Add basil and garlic and sauté for an additional 2 minutes. Add vinegar, stir quickly to combine, and remove from heat.
Spread cheese evenly over the bottom of the pie crust. Arrange the vegetables evenly over the cheese, and arrange the tomato slices attractively on top. Stir egg mixture and carefully pour into the prepared pie crust. Place the pie pan on a cookie sheet and bake on the middle rack of the oven for 10 minutes. Reduce heat to 325°F and cook for approximately another 20 minutes. The eggs should jiggle only slightly when poked, and may even start to puff a little. The crust will be a medium to deep golden brown.
Yield: 8 servings