Marinate the chicken in buttermilk for at least 30 minutes.
Prepare the coating by mixing flour, garlic powder, paprika, salt, and pepper in a bowl.
Remove the chicken from the buttermilk and dredge it in the seasoned flour mixture.
Heat oil in a deep skillet over medium-high heat for frying.
Fry the chicken breasts until golden brown and cooked through, about 5-7 minutes per side.
While the chicken cooks, toast the slices of bread.
Assemble the sandwich: place chopped romaine on the bottom slice, add the crispy chicken, drizzle with Caesar dressing, and top with Parmesan cheese.
Top with the second slice of bread, slice, and serve immediately.