1. Preheat the broiler. Rinse and dry the tomatillos. Line a broiler pan with foil and arrange the tomatillos on the foil along with the poblano and serrano chill peppers. Broil until they are charred on top, about 3 minutes. Use tongs to turn and broil the other sides until charred, 3 to 4 minutes.
2. Wrap the tomatillos and peppers in foil and let them rest for 10 minutes. Unwrap the tomatillos and peppers and peel the skin off the poblano chilli and remove the seeds. The tomatillos and jalapeno don’t need to be peeled or seeded.
3. Place the tomatillos and peppers into the bowl of a food processor. Add the garlic, sugar and salt. Pulse the mixture until the ingredients are coarsely chopped.
4. Add 5 to 6 tablespoons of water, the onion, and cilantro. Pulse quickly until a coarse puree forms then transfer the salsa to a serving dish. Makes about 1 3/4 cup.