Start by marinating the chicken in buttermilk for at least one hour, preferably overnight.
In a shallow bowl, combine flour, garlic powder, salt, black pepper, and oregano.
In another bowl, place the breadcrumbs.
Heat oil in a deep skillet over medium-high heat until shimmering.
Dredge each piece of chicken in the flour mixture, shaking off excess, then dip in the breadcrumbs.
Carefully place the breaded chicken in the hot oil, cooking in batches if necessary.
Fry until the chicken is golden brown and cooked through, about 5-7 minutes per side.
Remove the chicken from the oil and let it drain on paper towels.
To assemble the sandwich, spread Caesar dressing on each slice of bread.
Layer on chopped romaine lettuce, fried chicken, and a sprinkle of Parmesan cheese.
Top with the other bread slice, press gently, and serve.