Ground chicken simmers with diced vegetables and a compact tomato sauce for these four sandwiches. Reduce the filling until it holds together on a bun, then add toppings at serving. Use a temperature check for the ground poultry. Dice onion and pepper small so the filling sits on the bun without large pieces falling out. Break ground chicken into crumbles as it cooks; do not press it into one dense mass. Start with two teaspoons of Cajun seasoning and taste only after the meat is fully cooked. The archived corn-and-crushed-tomato version has different proportions and is not a direct addition to this four-bun formula. Simmer until a spoonful holds together without a puddle of sauce beneath it. Toast buns shortly before serving and keep cold slaw or lettuce separate until assembly.