Use a knife to cut away the flesh from the seeds and stems of the jalapenos. Reserve the seeds to adjust the spiciness later on.
If you are sensitive to spiciness, cut away the white membrane from the jalapeno flesh and discard.
Cut the jalapenos into large pieces. At this point you should have about 6oz of clean jalapeno.
Warm up 2 tbsp of vegetable oil in a saute pan over medium-high heat and sautee the onion for about 1-2 minutes, or until they just begin to soften.
Add the sliced jalapenos and cook for another 3-4 minutes while stirring. Jalapenos and onions should be softening up and have just a tiny bit of color on them.
Add the garlic and cook everything for 1-2 more minutes. When you are done cooking, the vegetables should be slightly softened and have a little bit of color on them.
Place the onions, peppers, and garlic on a plate and put in the refrigerator or freezer until cold (but not frozen).
Wash and dry cilantro leaves if necessary.
When the cooked vegetables are chilled, place them in the blender along with all of the other sauce ingredients. Blend very well but do not blend so long that the sauce begins to get too warm.
Sauce should be bright green and have a nice sauce consistency. Taste the sauce for spiciness, If you want it to be spicier, blend in small amounts of the reserved jalapeno seeds until it is at your desired spice level. Sauce should be very well seasoned and a bit tangy. Adjust seasoning with additional salt and lime juice if necessary. This will yield more sauce than is necessary for the dish. Leftover sauce will keep for 3-4 days in the fridge.