1 lb. lean ground beef (use ground beef with less than 10% fat for South Beach Diet)
1 T fish sauce (I like Three Crabs Fish sauce by far the best)
1-2 T Sriracha Sauce (depending on how much heat you want)
1 T water
zest from one large lime
juice from one large lime (about 1 1/2 T juice)
1/4 cup thinly sliced green onion (or double that amount if you're not using the cilantro)
1/2 cup chopped cilantro
1-2 heads iceberg lettuce
Heat the oil in a heavy frying pan, then saute the beef until it's cooked through and starting to brown, breaking apart with a turner as it cooks.
While beef cooks, mix together the fish sauce, Sriracha Sauce, and water in a small bowl. Zest the skin of the lime and squeeze the juice. (You may need two limes to get enough juice, but only use the zest from one lime.) Thinly slice the green onions and chop the cilantro. (Most iceberg lettuce doesn't need washing, but if yours does break the heads apart gently and wash and dry the lettuce.)
When the beef is done, add the Sriracha Sauce mixture and let it sizzle until the water has evaporated, stirring a few times to get the flavor mixed through the meat. Turn off the heat and stir in the lime zest, lime juice, sliced green onions, and chopped cilantro.
Serve meat mixture with iceberg lettuce leaves to fill with meat and wrap around it, to be eaten with your hands.