Spread the mayonnaise over each slice of bread. Place a piece of lettuce onto one slice and top it with the meat, tomatoes, any additional fillings, cheese and bread. Butter both sides.

In a medium non-stick pan, grill the sandwich for 2 minutes before flipping and grilling an additional 2-3 minutes, or until both sides are golden and crisp.

Remove the sandwich from the pan, and allow it to cool down to room temperature before cutting it in half.