1 teaspoon neutral oil, like canola
10 asparagus stalks, tipped and cleaned
1 large leek, cleaned and thinly sliced
2 tablespoons unsalted butter
1/4 cup all purpose flour
1/2 cup whole milk
1/2 cup heavy cream
1/4 cup gruyere, shredded
2 large eggs, lightly beaten
salt and pepper
freshly grated nutmeg
1 tart shell, blind baked (i use this one)
2 tablespoons fresh dill or parsley, chopped
add oil to a large skillet and place over medium heat. cook leeks and asparagus for 5-8 minutes, until leeks are translucent and asparagus is crisp-tender. set aside to cool
meanwhile, in a large sauce pan, melt the butter over medium-low heat. add the flour and stir constantly for two minutes, until the mixture clings to the bottom of the pan and begins to smell nutty. whisking constantly, slowly whisk in the milk and cream. bring the mixture to a boil, cook for two minutes, then remove from heat. quickly whisk in the gruyere until completely smooth. allow to cool for several minutes.
whisk in the eggs, one at a time, until incorporated and mixture is smooth again. season with salt, pepper and nutmeg.
lay the asparagus down in the blind-baked tart shell in rows, sprinkling the leeks over top. pour the egg mixture over top, spreading it in an even layer.
bake until golden brown and a knife inserted in the center comes out clean, 45 minutes to an hour. let cool for 20 minutes. unmold and serve warm or at room temperature, sprinkled with fresh herbs.