Preheat oven to 425°.
Discard husks and stems from tomatillos. Cut each tomatillo in half. Combine tomatillos and next 5 ingredients in a bowl; toss well. Arrange tomatillo mixture in a single layer on a jelly-roll pan coated with cooking spray. Bake at 425° for 15 minutes or until tomatillos are tender.
Place tomatillo mixture in a food processor; pulse 13 times or until chopped. Pour mixture into a large nonstick skillet. Add broth; bring to a boil over medium-high heat. Stir in chicken; reduce heat, and simmer, uncovered, 10 minutes or until liquid is absorbed. Remove from heat; stir in lime juice and salt.
Warm tortillas according to package directions. Spoon about 1/2 cup chicken mixture on one-half of each tortilla, and fold in half. Top each taco with 1 tablespoon sour cream.