Prepare the chicken filling: In a small mixing bowl, combine the shredded chicken with 2 tablespoons of mayonnaise and the Dijon mustard. Stir until every strand of chicken is evenly coated – you should see a creamy, pale golden colour with no dry spots remaining. Season with a pinch of salt and pepper.

Toast the bread: Spread the softened butter evenly over one side of each bread slice. Place a large frying pan over medium heat and, once the surface shimmers gently, lay three slices of bread buttered-side down. Toast for 2-3 minutes until the underside turns a deep golden brown and you hear a satisfying sizzle. Flip and toast the other side for another minute, then repeat with the remaining three slices.

Build the first layer: Take one slice of toasted bread and spread a thin layer of mayonnaise on the inside. Top with a lettuce leaf, pressing it down so it lies flat, then layer on half the sliced tomato rounds. The tomatoes should feel firm but give slightly when pressed.

Add the protein layer: Spoon the entire chicken mixture onto the tomatoes, spreading it evenly to the edges. Place two slices of cheese on top, letting them curl slightly over the chicken. If using turkey slices, lay them flat over the cheese now.

Create the middle deck: Place a second slice of toasted bread on top of the cheese. Press down gently with your palm – you'll feel the layers compact slightly. Spread mayonnaise on the top of this bread, then add another lettuce leaf and the remaining tomato slices. Season with a pinch of salt.

Cap and secure: Place the final slice of toasted bread on top, buttered-side up. Insert four long cocktail sticks through the sandwich at even intervals – you should feel them pierce through all three layers with a clean pop. Using a serrated knife, cut the sandwich diagonally from corner to corner, then repeat the other way to create four triangles. The filling should stay neatly in place, and you'll see the beautiful cross-section of colours: golden bread, green lettuce, red tomato, and creamy chicken.