Whisk together mayonnaise, rice vinegar, and honey in a bowl until smooth, then set aside
Heat a small skillet over medium heat and combine water and brown sugar
Simmer the mixture, then add the walnuts
Reduce heat and stir continuously until the syrup thickens and coats the walnuts
Transfer the walnuts to a parchment-lined plate to cool
Pat the shrimp dry with paper towels
Beat the egg in a small bowl
Place cornstarch in a separate shallow bowl
Dip each shrimp into the cornstarch, shaking off any excess
Dip the shrimp into the beaten egg
Coat the shrimp in cornstarch again
Set aside on a plate or baking sheet and repeat with the remaining shrimp
Preheat the air fryer to 400°F (200°C)
Lightly coat the bottom of the air fryer basket with oil
Arrange the shrimp in a single layer in the basket without overcrowding
Brush or spritz the shrimp lightly with oil
Cook for 5 minutes
Flip the shrimp and cook for an additional 3-4 minutes until crispy and fully cooked
Check the shrimp with a digital thermometer to ensure doneness
Toss the cooked shrimp with the sauce and caramelized walnuts until evenly coated
Garnish with sliced green onion if desired
Serve immediately and enjoy