Cut the bread into quarters, then cut each quarter in half horizontally.
In a bowl, mix the mayonnaise, olive oil, Parmesan, lemon juice and anchovies (if using). Finely grate the garlic clove into the mixture and season with a little sea salt if necessary (the anchovy is quite salty), and black pepper. If you prefer the dressing a little runnier, add more oil.
To make the sandwiches, spread the dressing onto the bottom of the foccacia quarters, then layer up the sandwich with the lettuce, more caesar dressing, slices of golden turkey breast and avocado slices. Finish off the top of the sandwich with a little more dressing, shavings of parmesan and a good amount of black pepper. Top with the remaining focaccia quarters.