# What You'll Need:
→ Crispy Onions
01 - 1 small yellow onion, thinly sliced
02 - 1/2 cup all-purpose flour
03 - 1/4 cup cornstarch
04 - 1/2 teaspoon salt
05 - 1/2 teaspoon black pepper
06 - 1/2 teaspoon paprika
07 - 1/2 cup buttermilk (or milk with 1 teaspoon lemon juice)
08 - Vegetable oil, for frying
→ Sandwich Assembly
09 - 4 slices sourdough or white bread
10 - 4 tablespoons unsalted butter, softened
11 - 1 cup grated sharp cheddar cheese
12 - 1 cup grated mozzarella cheese
# Cooking Steps:
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 and transfer to a plate.
03 - Heat 1 inch vegetable oil in a large skillet over medium-high heat to 350°F. Fry onions in batches for 2-3 minutes until golden brown and crispy. Drain on paper towels.
04 - Spread softened butter evenly on one side of each bread slice.
05 - Place two bread slices butter-side down. Divide cheddar and mozzarella evenly between slices. Top with crispy fried onions, then remaining cheese. Cover with remaining bread slices, butter-side up.
06 - Heat a nonstick skillet or griddle over medium-low heat. Cook sandwiches for 3-4 minutes per side, pressing gently with a spatula, until bread is golden brown and cheese is fully melted.
07 - Remove from heat and let rest for 1 minute. Cut each sandwich in half diagonally and serve immediately.