(Makes 2 tarts)
1 package puffed pastry sheet
1 TBS olive oil
2 TBS butter
4 large leeks, white and light green part sliced into half moons
2 onion, sliced into half moons
1 1/2 cup Gruyere cheese, shredded (Swiss cheese also works well)
chives for garnish
Preheat oven to 400 degrees.
On a floured work space roll out puffed pastry sheet to fit a fluted tart tin with a 1/2 inch overhang. Fit the pastry into the pan and fold under the overhang, pressing into the sides of the pan.
If you don't have a tart pan this can be made free form too. Just roll dough out to a 7x 14 inch triangle.
Score the inside edges of the tart and prick the center.
Refrigerate for 15 minutes, then bake for 15 minutes. When the tart is removed from the oven, reduce the oven to 375 degrees.
Meanwhile, put oil and butter into a large skillet and heat over a medium heat. Add onions and leeks. Cook over medium heat until wilted, about 5 minutes. Reduce heat and cook until tender, about 15 minutes.
When tart is removed from the oven, gently push the center down SLIGHTLY if it has puffed. Sprinkle on 1/2 of the cheese over each tart, avoiding the edges.
Spoon 1/2 of the leek mixture over each tart, avoiding the edges.
Bake for 10 minutes, until the cheese is melted.
Cut into wedges and serve.