For the wings: Fill a large, wide pot with about 1 1/2 inches of oil and bring it to 375 degrees F on a deep-fry thermometer. Toss the chicken wings with the cornstarch and 1/2 teaspoon salt in a large bowl.
Fry half of the wings until golden brown and crisp, about 16 minutes, then transfer to a paper towel-lined tray. Bring the oil back up to 375 degrees F and fry the remaining wings.
For the sauce: While the wings cook, melt the butter in a small saucepan over medium-high heat. Add the garlic, scallion whites and ginger and cook, stirring, until golden, about 2 minutes. Add the hoisin, honey, soy sauce, vinegar and sambal oelek and bring just to a simmer. Remove from the heat.
Put the wings in a large bowl and drizzle with the sauce. Add the scallion greens and toss to coat. Serve immediately.