1 sheet puff pastry
1 egg, beaten
3 tablespoons olive oil, divided
2 medium onions
2 sprigs of thyme
kosher salt and freshly ground black pepper
3 tablespoon chopped herbs such as parsley, tarragon or dill
2oz grated Gruyère
1lb medium or thick asparagus, trimmed and stems peeled*
8 oz farmers cheese or other fresh cheese such as goat cheese or ricotta
Preheat the oven to 375º F.
Place the defrosted puff pastry on a lightly floured work surface. Gently roll it out into a rectangle about ⅛-inch thick. Place on a parchment lined baking sheet. Use a paring knife to score a ½-inch border around the edge of the pastry. Dock the dough all over with a fork, avoiding the border. Briskly beat the egg with the fork, then brush the border with the egg wash. Save the remaining egg. Place the pastry in the fridge.
Heat 2 tablespoons of the olive oil in a large, wide skillet or Dutch oven. Add the onions and the thyme sprigs. Season with ½ teaspoon salt and a few grindings of pepper. Cover and cook over low heat until soft and wilted. Turn up the heat and caramelize the onions lightly, being careful not to burn them. Remove from heat and allow to cool.
Set up a steamer and steam the asparagus for about 2 minutes. Remove from the steamer and allow to cool. Toss with the remaining olive oil and season with salt and pepper.
Place the cheese in a bowl and season with salt and pepper. Add the chopped herbs, the Gruyère and the remaining egg. Beat with a wooden spoon to soften. Remove the dough from the fridge. Spread the cheese over the pastry evenly, within the borders.
Spread the cooled caramelized onions over the cheese and then arrange the asparagus on top, alternating directions of the spears to form a pattern.
Chill for another 20 minutes. It can be made ahead to this point and can be wrapped and refrigerated for a day.
Bake the tart for 10 minutes. Turn the sheet pan, and bake for another 15 to 20 minutes, until the crust is deep golden brown and cooked through. The dough may be golden on top but make sure it is thoroughly cooked though.
*It is not necessary to peel the asparagus stems but it looks prettier!
