# Directions:
01 - Combine flour, cornstarch, salt, pepper, and paprika in a shallow bowl. Pour buttermilk into a separate bowl.
02 - Dip onion slices into buttermilk, then press into flour mixture. Shake off excess coating.
03 - Heat 1 inch vegetable oil in skillet over medium-high heat. Fry onions in batches 2–3 minutes until golden and crispy. Drain on paper towels.
04 - Spread softened butter on one side of each bread slice.
05 - Place two bread slices butter-side down. Distribute half the cheddar and mozzarella over each. Add crispy onions, then remaining cheese. Top with remaining bread, butter-side up.
06 - Cook on nonstick skillet or griddle over medium-low heat 3–4 minutes per side, pressing gently, until bread is golden brown and cheese melts.
07 - Let rest briefly, cut in half, and serve hot.