Start by toasting the bread then remove the crusts. No need to butter as the mayonnaise will suffice.
To assemble : Place one round of toast on the bottom, and spread with mayonnaise. Place lettuce, tomato, egg and bacon and top with another slice of toast. Spread generously with mayonnaise on the top and season with salt and pepper. Add the cheese slice, onion and chicken.
Spread the underside of the remaining toast with mayonnaise and place on top to form a triple layer sandwich.
Add a toothpick to each corner side of the sandwich and carefully cut on the diagonal one way and then across the other way so that you have 4 diamond slices with a toothpick holding each in place. Arrange on an angle on the plate and serve with a small bowl of crisps on the side of the plate.
I make ahead the bacon, eggs and chicken. All that needs to be done is toasting the bread and assembling. Easy peasy!