This quiche is unusual in that it has lots more vegetables than it does custard.  If the sides of  your tart pan are not very high or if your crust has shrunk, you might not be able to get all the custard into the pan.  If you think you've got a short-sided crust, make a smaller amount of custard using 1/2 cup heavy cream and 1 egg.

Ingredients:

1 tablespoon butter
2 stalks celery, peeled, trimmed and cut into small dice
2 slender leeks, white and light green parts only, trimmed, quartered lengthwise and finely sliced
2 slender carrots, peeled, trimmed and finely diced
1 medium red pepper, trimmed, seeded and finely diced
2/3 cup heavy cream (see above)
1 large egg
1 large egg yolk
1/3 cup grated cheese, such as Gruyere, Parmesan or cheddar
Salt and freshly ground pepper

One 9- to 9 1/2-inch partially baked tart shell still in its pan.

Put a skillet over medium-low heat, add the butter and, when it's melted, toss in the vegetables. Cook, stirring, for about 10 minutes, or until the vegetables are tender. Season with salt and pepper, then scrape the vegetables into a bowl and let them cool while you preheat the oven.
When you're ready to bake the quiche, center a rack in the oven and preheat the oven to 400 degrees F.
Put the partially-baked crust on a lined baking sheet.
Spoon the vegetables into the tart shell and spread them evenly along the base of the crust - the vegetables will just about fill the crust. Whisk the cream, egg and egg yolk together, season with salt and pepper and carefully pour the custard mixture over the vegetables. Depending on how your crust baked, you may have too much custard - don't push it. Pour in as much custard as you can without overflowing the sides of the crust, wait a few minutes until it's settled into the vegetable's nooks and crannies then, if you think it will take it, pour in a little more. Very carefully slide the baking sheet into the oven.  (If it's easier for you, put the quiche into the oven without the custard, then pour in the cream.)
Bake the quiche for 20 minutes, sprinkle the cheese over the top and bake for another 10 to 15 minutes, or until the cheese is golden and, most important, the quiche is set and uniformly puffed (wait for the center to puff). Transfer the quiche to a rack and cool until it's only just warm or until it reaches room temperature before serving.