Preheat oven to 425ยบ F. Mix together ingredients for sandwich spread in a medium bowl until well-combined. Set aside.
Slice loaf of French bread in half lengthwise and place on a rimmed baking sheet.
Spread the inside of both halves of bread liberally with the sandwich spread.
Begin layering ham, cheese, and lettuce onto one half of the bread. Top with the other half of bread and place into the preheated oven for 5 minutes, or until the sandwich has heated throughout and the cheese has reached the melting point you prefer.
Remove from oven and slice in the middle. Then, slice each of the halves in half again until you have four pieces.