Melt butter in medium saucepan on medium-high heat. Add onions; cook 2 min. or until crisp-tender, stirring frequently. Stir in flour until blended.
Add tomatoes, broth and seasoning mix; stir. Bring to boil; simmer on medium-low heat 2 min. Add chicken and VELVEETA; cook and stir 5 min. or until VELVEETA is completely melted and chicken is heated through.
Top with crushed chips. Serve with lime wedges.