Combine the mustard and mayonnaise. Mix well. Set aside.
Toast the bread slices in the way that you prefer.
Spread the mayonnaise mixture equally on both bread slices.
Assemble the sandwich by placing a slice of bread on a flat surface (side with mayo facing up). Top with lettuce leaf, tomato slices, bacon, and avocado slices. You can even add cheese if preferred.
Top the avocado with the other slice of bread. The side with mayo spread should be facing down.
Serve with your favorite drink.
Share and enjoy!