Tomatillos are Mexican green tomatoes in husks. In place of fresh tomatillos, you can use 3 cans (12 oz each) whole tomatillos. Drain liquid, and reduce salt to 1 teaspoon total. Salsa made with canned tomatillos will gelatinize when refrigerated. Stir well; it loosens up at room temperature.
Use leftover grilled chicken breasts for another meal: Place strips of onion and bell peppers in a grill basket and grill alongside the chicken. (If chicken was previously grilled, just heat throughout.) Cut grilled chicken breasts into strips and mix with the salsa verde. Place grilled chicken, onion and bell peppers in warm tortillas. Serve with sour cream.