Cook chicken breast in shallow pan in 350 degrees oven for 1 to 1 1/2 hours. Before baking sprinkle liberally with garlic salt and soy sauce. Dot with several tablespoon of butter. Cool chicken and cut in bite sized pieces. Mix with shredded cheddar cheese, chopped purple onions, chopped tomatoes, and shredded lettuce. Mix just enough Hellmann's mayonnaise to hold mixture together. Serve in pocket breads.