Heat oven to 400°F. Spray 8-inch skillet with cooking spray. Add beef and onion; cook over medium-high heat, stirring frequently, until beef is thoroughly cooked. Drain.
Stir in frozen mixed vegetables, brown sugar, mustard, chili sauce and Worcestershire sauce. Cook 2 to 3 minutes, stirring occasionally, until vegetables are crisp-tender.
Spoon beef mixture into 2 (1 1/2-cup) ungreased ovenproof bowls or ramekins. Top each with frozen biscuit. Brush each biscuit with milk; sprinkle with sesame seed.
Bake 20 to 25 minutes or until biscuits are deep golden brown.