In a large, heavy-bottomed pot, combine oil and onions over medium-high heat. Cook, stirring occasionally, until onions are thoroughly browned, 15 to 20 minutes (the darker you can get them, the better, but don't let them burn).
Reduce heat to medium and stir in cumin, garam masala, cayenne, pepper, salt, and tamarind paste. Cook, stirring constantly, until onions are thoroughly coated, about 2 minutes. Add chickpeas and stir to coat thoroughly. Reduce heat to low, cover, and cook until heated through, about 3 minutes. Season to taste with salt.
Mix greens well and divide among wide, shallow bowls. Spoon about 1 cup chickpeas over greens.
*Garam masala, a northern Indian spice blend, is available at well-stocked grocery stores and Indian markets, as is tamarind paste (check the label to be sure that it has no added sugar). The paste should have the consistency of loose applesauce; if it's runnier, add another tablespoon of it to the dish.
Variations: Instead of chickpeas, switch in an equal amount of eggplant, chicken, or tofu.
Note: Nutritional analysis is per serving without Winter Greens.