Salsa de tomates verdes:
1 lb. tomatillos, husks removed
serrano chiles, 1 for mild, 2-3 for medium, 4+ for hot (of course it all depends on the luck of the draw)
2-3 cloves garlic
1/2 small white onion, chopped
about 1/3 cup chopped cilantro - a small handful
salt
Boil the tomatillos and chiles for a good 7-10 minutes, until the tomatillos have changed color. Puree them in a blender along with the garlic. Add the onion, cilantro, and salt. Chill, then enjoy.
To make it a bit milder, add some finely diced avocado. The flavors blend really well, and the avocado takes the spice down a notch.
Another great variation is to add a bit of toasted and ground pumpkin seed (as you would with pipian). It really changes the flavor and texture of the salsa.
Salsa Mexicana:
6 roma tomatoes, cores + seeds removed
serrano chiles, more or less same formula as with the salsa verde
1/2 small white onion
1/3 cup chopped cilantro - again, about a handful
juice of 1 lime
salt
Chop everything as absolutely finely as you possibly can without turning it to mush (especially the tomatoes). The finer, the better - the texture is better and it's more impressive. If I'm really set on making a great batch, I'll spend about 45 minutes chopping. Once you've mixed all the ingredients, let it sit for about an hour for all the flavors to fully mix.