Brush chicken with browning sauce and arrange on rack around outside edges of circular microwave dish. Cover loosely w/waxed paper and microwave on high for 6 mins. Remove chicken from rack and place in bottom of dish, turning breasts over and keeping them in a circle around edge of dish. Sprinkle with 1/2 tspn of salt and 1/4 tspn of pepper. In small bowl, mix together yogurt, onion, and mustard; spoon over chicken, dividing equally on each piece. Cover loosely w/waxed paper and microwave on high 6 mins. Or until fork can be inserted in chicken with ease. Sprinkle with remaining salt and pepper. Let stand 2 mins. Then remove to warm serving platter.