Grill chicken breasts, allow to rest 5 minutes and slice thin. Heat tacos over grill about 20 seconds per side or in oven. Cover to keep warm.

Combine sour cream and chipotle chile in bowl, season with salt and pepper. In a large bowl, whisk lime juice, cilantro, Worestershire sauce and brown sugar. Add the sliced chickenn breasts and toss so each piece is covered.

Serve chicken with tomatoes, avocados and sour cream mixture.