1. Heat a large pot of salted water to boiling. Ready a colander in sink and line a work surface with 2 thicknesses of paper towels.
2. To prepare the greens, cut out the core of the cabbage with a paring knife. Gently pull off 6 to 8 of the largest outer leaves, trying not to tear them. Strip the leaves from the stalks of the chard (the stems are delicious sauteed in oil and garlic as a side dish) and wash the leaves thoroughly. Stem and thoroughly wash the spinach. (Chard and spinach tend to be muddy and/or sandy, so be sure to wash both carefully.) Place the grated zucchini in a mixing bowl and sprinkle with a generous amount of kosher salt. Toss to mix and transfer to a colander. Let stand 10 minutes. Press the zucchini against the colander to extract as much moisture as possible. Rinse well under cold water and squeeze again.
3. To blanch the greens, submerge the cabbage leaves in the boiling water and stir gently to separate. Blanch until softened and the color brightens, about 4 minutes. Remove them gently to the colander (a wire skimmer works well) and rinse under cold water. Squeeze gently and transfer to the paper towels to drain. Cut out the thickest part of the center portion. When the water is boiling, stir in the chard (or dandelions). Cover the pot and let the water return to a boil. Stir in the spinach and continue stirring until the chard is tender, about 3 minutes. Drain the greens in the colander. Rinse the greens under cold running water until cool enough to handle. Squeeze them out by hand, in small batches, to extract as much liquid as possible. (This is important-if the greens are watery, the finished tart will be bland and difficult to cut.) Chop the greens very fine. (If you have a food processor, use it to chop the greens.)
4. Trim the root ends of the leeks and cut the leeks in half lengthwise. Rinse thoroughly under cold running water to remove all the sand from between the layers. Slice crosswise 1/4 inch thick.
5. Heat the oil in a heavy large skillet. Stir in the zucchini and leeks and sprinkle with salt. Reduce the heat to very low and cover the skillet. The heat should be low enough to draw the liquid out of the vegetables without browning them. Cook the vegetables, stirring once or twice, until the leeks are tender, about 10 minutes. Increase the heat to medium and stir in the minced greens. Cook until the liquid is evaporated without browning the vegetables. Transfer to a mixing bowl and let cool.
6. Beat in the ricotta, Parmesan cheese, eggs, egg yolk, lemon juice, salt, pepper and nutmeg. Taste for seasonings and adjust as necessary.
7. Line the bottom of a 9 inch round cake pan (nonstick works well) with the largest best-looking cabbage leaf. Arrange enough of the remaining cabbage leaves, slightly overlapping around the sides with the excess hanging over the sides, to cover the bottom and sides of the pan completely. Spoon the filling into the pan and smooth it into an even layer. Fold the overhanging leaves over the filling and smooth. If necessary, cover any exposed filling with leftover cabbage leaves. Bake until the top is lightly browned and the filling is set, about 45 minutes. Invert onto a serving plate and cool about 5 minutes before serving. The torte is also delicious at room temperature.Makes 8 servings
Per Serving: 222 Calories (44.0% from fat); 12g Fat (5g Sat, 5g Mono, 1g Poly); 15g Protein; 18g Carbohydrate; 6g Dietary Fiber; 97mg Cholesterol; 654mg Sodium. Food Exchanges: 1 1/2 Lean Meat; 3 Vegetable; 1 1/2 Fat.