Clean 2 leeks and thinly slice into half rounds or julienne. Mince green garlic to make 1/2 C. Rinse 6 crimini or other gourmet mushroom and slice. Place the leeks and mushrooms in a baking dish. Toss with 2 T. olive oil, salt and pepper. Bake at 350 until the leeks are soft, then add 1/4 C. vegetable or mushroom broth and cook another 30 minutes until caramelized and very soft.
In a food processor, combine 2 1/2 C. flour and 1/2 t. salt. Cut 1 cold stick of butter into pieces and add to the flour along with 1 egg and 1/4 C. very cold water. Pulse until the dough resembles coarse crumbs. Wrap in plastic or wax paper and refrigerate for at least half an hour.
Shell peas to make 1/2 C. or trim 1/2 C. Snap Peas and cut into small pieces. Add to the leeks when you remove them from the oven.
Make small balls of dough and roll them into softball-sized circles. Place a tablespoon or two of leek filling in the middle of each and fold it over, pressing the edges together. Use a little egg white to help the dough stick, and then brush the empanadas with the beaten egg yolk.
Bake at 400 degrees until the empanadas are golden brown.
Serve the empenadas with a salad and Chimichurri sauce for dipping.