In a large bowl, toss together cabbage and leeks, squeeze firmly 4 or 5 times to wilt them slightly. Add flour or matzo meal, salt, pepper and eggs and stir until well coated. Heat a large skillet over medium heat and spray generously with oil. Working in batches, drop a generous 1/3 cup of the cabbage mixture into skillet, spreading it out to make 4 inch pancakes. Spray the tops with oil and cook, flipping once, until tender and deep golden brown, 8 - 10 mins