Toss together the cornmeal, flour, and salt and pepper in a shallow pan big enough to hold a single fish. Heat up equal parts of butter and olive oil in a large cast-iron skillet. Wait until the pan and the fats are very hot, then coat the fish with the cornmeal mixture and put the fish in the skillet. Cook for roughly 2 minutes, or until it turns a crispy golden brown. Flip the fish and cook another 30 seconds on the second side. Eat at once.