Leek and Celery Pie

Ingredients

• 0.3 teaspoon pepper black
• 3 cups celery finely chopped
• 3 large eggs 
• 1 cup greek feta crumbled (preferably Mt. Vikos or Dodoni brand)
• 0.5 cup optional: dill fresh chopped
• 0.7 cup flat-leaf parsley fresh chopped
• 1 cup mint leaves fresh chopped
• 10 cups leeks white green finely chopped ( and pale parts only)
• 0.3 cup olive oil extra-virgin
• 1.5 oz parmigiano-reggiano cheese finely grated ()
• 1 tablespoon red-wine vinegar 
• 1 teaspoon salt 
• 0.5 cup whole-milk yogurt (preferably Greek)
• 0.8 cup water 

Equipment

• bowl
• frying pan
• oven
• knife
• pot
• plastic wrap
• baking pan
• ziploc bags
• rolling pin
• colander

Directions

1. Stir together flour and salt in a large bowl, then make a well in center and add water, yogurt, 1/2 cup oil, and vinegar. Stir until a soft dough forms, then knead on a work surface (do not dust with flour) until smooth and pliable, about 4 minutes. Form dough into a ball and put in an oiled bowl, then turn to coat. Cover bowl with plastic wrap and let dough stand at room temperature 1 hour.
2. Wash leeks in a bowl of cold water, agitating them, then lift out and drain well in a colander.
3. Heat 1/4 cup oil in a deep 12-inch heavy skillet or a 5- to 6-quart heavy pot over moderately high heat until hot but not smoking, then sauté leeks and celery with 1/2 teaspoon salt, stirring frequently, until softened and translucent, 10 to 12 minutes.
4. Transfer to a bowl and cool, stirring occasionally, 10 minutes.
5. Put oven rack in middle position and preheat oven to 375°F.
6. Stir herbs into leek mixture along with cheeses, pepper, and remaining 1/2 teaspoon salt. Lightly beat eggs with remaining 3 tablespoons oil in a small bowl, then stir into leek filling.
7. Brush baking pan with 2 tablespoons oil.
8. Divide dough in half.
9. Roll out 1 half on a floured surface with a floured rolling pin into a 19- by 14-inch rectangle. Fold rectangle loosely into quarters and transfer to baking pan, then unfold dough and fit into pan, leaving a 1-inch overhang.
10. Spread filling evenly in pan.
11. Roll out remaining dough on floured surface with floured rolling pin into a 20- by 15-inch rectangle. Lift dough and drape it over filling, leaving it slightly wrinkled.
12. Roll edge of bottom crust over top to form a rope edge all around pie.
13. Brush top of pie with remaining 2 tablespoons oil. Score top crust into serving pieces with a sharp knife (mark crust but do not cut through it).
14. Bake pie until golden brown, 50 to 60 minutes. Cool to room temperature in pan on a rack, about 1 hour.
15. · Dough can be made 3 days ahead and chilled in a sealed plastic bag. Bring to room temperature before rolling out.· Pie can be baked 4 hours ahead and kept at room temperature.