Heat oven to 350°F. Place oven rack in upper middle position.

Combine all sauce ingredients in bowl; set aside.

Combine chicken, 1 teaspoon soy sauce and 1 teaspoon sesame oil in bowl; set aside.

Combine remaining 1 teaspoon sesame oil, eggs, pepper and salt in bowl; beat with whisk. Set aside.

Melt 1 tablespoon butter in 10-inch nonstick ovenproof skillet over medium-high heat until sizzling; add chicken strips.

Cook, stirring occasionally, 2-3 minutes or until chicken is no longer pink. Remove chicken; set aside.

Add 1 tablespoon butter to same skillet; add bell pepper, green onions and bok choy.

Cook over medium-high heat 2-3 minutes or until vegetables just begin to soften. Remove vegetables; set aside.

Melt remaining 1 tablespoon butter in skillet over medium heat until butter is sizzling.

Add chicken and vegetables to egg mixture; pour egg mixture into skillet.

Cook, stirring and lifting around bottom edges with spatula, 1-2 minutes or until eggs just begin to set.

Place skillet into oven; bake 8-10 minutes or until eggs are set.

Carefully place large plate over skillet; turn skillet to release frittata onto plate. Serve with reserved sauce.