Next, we zest the lemon over a piece of wax paper using our microplane. We have 1 teaspoon of zest. We squeeze the lemon halves into a measuring cup, discarding the seeds. We have 2 tablespoons of lemon juice. We combine the lemon juice, zest, mustard, some salt and pepper, and the olive oil in the measuring cup. Using scissors, we slice the sage leaves into the marinade.
We pour the mixture over the chicken breasts, seal the bag, and smoosh around the marinade. We set it aside in a bowl for 20 minutes.
We pre-heat our gas grill.
While the chicken is marinating, we cover our grilling brick with heavy duty aluminum foil.
We cut our bread in half lengthwise, and then slice almost all the way open. We have our cheese grated and the sliced ham ready.
Discarding the marinade, we grill the chicken on the hot grill for about 5 minutes per side. The chicken should be just cooked through.
We remove the chicken to a clean platter and let rest for a few minutes. Not all of the chicken will be used in the sandwiches—the rest will be used for other sandwiches and salads for a couple of lunches!
We slice two of the chicken breasts and layer it in the bread with the provolone and ham.
We put the sandwiches on the grill, one at a time, weighting them down with the brick facing the open sides of the sandwich so as to try and keep the ingredients inside. We cook for a few minutes on the one side, carefully remove the brick, flip the sandwich, and weight again. We keep them on the grill until the crust is toasty and the cheese is melted. We repeat with the remaining sandwich.
Each sandwich is sliced in half. We serve one or two per person, with mayonnaise if desired.