Preheat your oven to 350.
Heat a Tbs. of oil in a medium skillet over medium. Season the chicken all over with a good pinch of salt and the Italian seasoning. Sear in the pan for five minutes per side, until cooked through and blackened all over. Let the chicken rest for about five minutes before chopping up as finely as you can.
Once chopped, stir in the mayonnaise.
Place the French breads on a rimmed baking sheet. Take a sharp knife and score it right down the center. Using your fingers, sort of pull the bread away from itself, creating a canoe-like well down the center. Spoon the chopped chicken down the center of each French bread, then top with sliced tomato and onion. Layer the cheese over the veggies. Brush the egg wash over the exposed dough, to help create a shiny golden crust. (I said “down the center” like thirty times.)
Bake for 30 minutes, until the cheese melts and starts to brown in places, and the dough is slightly puffed and golden brown.
Slice and serve immediately!
Makes two loaves.
