Cut away the roots and most of the green part from the leeks and discard. Peel away any loose layers, cut the leeks in half lengthwise, and then cut crosswise into ½ -inch-wide pieces. Soak them in a sink full of cold water, swish them around to loosen any dirt, remove with a slotted spoon, and drain well in a colander. You will have about 6 cups chopped leeks. Put them in a saucepan with lightly salted water to cover, bring to a boil over high heat, reduce the heat to low, and simmer until the leeks are very tender, about 20 minutes. Drain well and squeeze out any excess moisture. You will have about 2 cups cooked leeks. Soak the matzohs or bread slices (remove the crusts) in water and squeeze dry.
In a large bowl, combine the leeks, soaked matzoh or bread, eggs, 1½ teaspoons salt, pepper, and the nuts, if using. Mix well and, if the mixture seems too moist, add matzoh meal until it holds together. You may then need a bit more salt. Form the mixture into patties about 2 inches in diameter and ½ to ¾ inch thick.
Pour oil to a depth of about 1 inch into a large sauté pan and heat to 350 degrees F on a deep-frying thermometer. Meanwhile, spread some matzoh meal on a plate and dip the patties in it, coating both sides and tapping off the excess.
When the oil is hot, add the patties, in batches, and fry, turning once, until golden on both sides, 6 to 8 minutes total. Using a slotted spatula or tongs, transfer to paper towels to drain briefly. Sprinkle with salt and serve piping hot with lemon wedges.