1. Whisk crushed saltines, flour, Old Bay, baking powder, and cayenne together in large bowl. Whisk seltzer, scallions, egg and yolk, mayonnaise, mustard, and hot sauce into saltine mixture until combined. Gently fold crabmeat into batter until well combined. Cover and refrigerate for at least 30 minutes or up to 2 hours.

2. Set wire rack in rimmed baking sheet and line half of rack with triple layer of paper towels. Add oil to large Dutch oven until it measures about 1 1/2 inches deep and heat over medium-high heat to 350°F.

3. Spray 1/4-cup dry measure with vegetable oil spray. Place 6 packed scoops of crab mixture in hot oil, using spoon to help dislodge batter from dry measure. Adjust burner, if necessary, to maintain oil temperature between 325 and 350°F. Fry until deep golden brown and hot throughout, about 5 minutes. Transfer crab fluff to paper towel-lined side of rack and let drain for 1 minute, then move to unlined side of rack. Return oil to 350°F and repeat with remaining crab mixture. Serve.

Makes 12