There are two variations to this recipe -- one where you roast the garlic, onion, and peppers before combining with everything else in the food processor and another where you just leave everything raw. Both are very tasty.
Wash, de-seed, and slice jalapeños and serranos into fourths (long slivers). Heat some olive oil in a frying pan (non-stick works too) -- when the pan is hot but not burning hot, add the pieces of pepper skin side down to the pan and saute them for a few minutes. When they soft and the skin starts to brown a little, remove from pan and cool.
Keep the pan hot and throw in the garlic cloves (skin still on) along with trimmed and halved green onions. Saute for a few minutes -- onions will soften slighted and be a bit seared and garlic skin will brown and cloves will get mushy. Remove from pan and let cool. Set pan aside.
Wash and dehusk the tomatillos. Then quarter each tomatillo and set to the side. Take the cilantro and trim off the ends (keep most of stem) and then cut the bunch into smaller portions (to fit the Cuisinart better).
Place half of the tomatillos in the Cuisinart and 'chop/pulse' until they are pureed to a slightly chunky liquid. Throw in some cilantro, the pieces of roasted jalapeños and serrano, the roasted green onions, and the peeled garlic cloves. Puree again until all combined. Add rest of tomatillos and juice of 2 limes. Add salt, pepper, red pepper flakes, and cumin (a pinch of each or so). Chop/pulse again.
Find a tortilla chip and taste your creation -- add more salt, pepper, red pepper flakes, & lime until you are happy. Transfer to a bowl/container and chill for a few hours before serving.
Variation 2: Skip the sautéing in the pan altogether. No olive oil needed.
Delicious with corn tortilla chips. Unbelievable on a hamburger hot off the grill. Enjoy!