1Toast the sourdough bread slices until golden brown.
Spread 1 tablespoon of spicy mayonnaise on one side of each slice of bread.
Place a leaf of iceberg lettuce on four of the bread slices.
Evenly distribute the grilled chicken breast over the lettuce.
Layer the sliced avocados on top of the chicken.
Add sliced red onions over the avocados.
Top with the remaining slices of bread, mayonnaise side down.
Cut each sandwich in half and serve immediately.