In a skillet over medium heat, saute sausage, leek, and garlic. (If you like things spicy, add a pinch or two of red pepper flakes.)
Separate one egg and set the yolk aside. In a mixing bowl, beat the egg white and remaining eggs. Mix in kale, mozzarella cheese, ricotta cheese, salt, pepper, nutmeg, lemon juice, and sausage mixture.
Line a deep 9 or 10-inch pie dish with bottom pastry (with a 9-inch dish you will likely have leftover filling). Add filling. Cover with top pastry. Trim, seal and flute edges. Cut slits in top. Beat water and remaining egg yolk; brush over top.
Bake at 425 degrees for 20 minutes, then lower heat to 400 degrees for another 30 minutes (cover pie edges with foil if getting too brown) or until crust is golden brown and filling is bubbly. Let stand for 10 minutes before cutting.