Fry the bacon in a pan for 5 minutes until crispy and then drain on a paper towel.
Fry the chicken breast for 7 minutes on both sides and season with salt and pepper.
In the meantime, mix the mayonnaise with the mustard to a fine measure and season with a little salt and pepper.
Toast all toasts until lightly crisp and spread with mayonnaise.
Slice the tomatoes and lettuce.
Cut the chicken breast into fine slices.
Spread lettuce on 8 slices of toast.
Place bacon and tomatoes on 4 of these toast slices over the lettuce.
On the remaining 4 slices, place the chicken breast over the lettuce.
Place the slices of toast with the chicken breast, toppings facing up, on top of the toast with bacon and tomatoes.
Finally, place the remaining slices of toast on top of the club sandwich with the mayonnaise facing down.
Using a sharp knife, you can now cut the American club sandwich in half diagonally into 2 or 4 halves and secure with a toothpick.