Warm tortillas according to package directions.
In large nonstick skillet, melt butter over medium-high heat; cook chicken, garlic and dried basil, stirring, just until chicken is browned all over.
Whisk flour into milk; gradually stir into skillet. Reduce heat to medium-low and cook, stirring, for about 5 min or until thickened and chicken is no longer pink inside.
Remove from heat; stir in Parmesan cheese, hot pepper sauce (if using) and pepper, stirring until cheese is melted. Spoon filling along centre of each tortilla; top with tomatoes and fresh basil (if using). Fold up bottom of tortilla, then fold in sides to enclose filling.