Flame roast poplano peppers until skins are black and well charred. This can be done on your gas stove, gas grill or under the broiler. Once charred, place in a metal bowl and cover with plastic wrap for 5 minutes. Rinse under cool water, removing charred skin, stem and seeds. Place flesh into blender.
Bring a small pan of water to boil. Boil tomatillos and jalapenos for 3-4 minutes. Remove with slotted spoon and place in blender.
Squeeze juice of 2 limes into blender. Add garlic, onion, cilantro, vinegar, cumin and salt. Blend to desired consistency.
With blender running, drizzle olive oil in a thin stream. Use as little oil as none to up to a 1/2 cup for a classic vinaigrette ratio. Adjust seasoning to taste.
Notes
Yield = 3-4 cups Store in refrigerator for up to a week.