Heat oven to 375°F. Spray a 4-quart saucepan with vegetable cooking spray, add chicken, and cook over medium-high heat until browned. Remove chicken and set aside.
In same saucepan, melt butter over medium heat. Add onion and cook 3 minutes, or until softened. Add flour and cook for 1 minute. Gradually whisk in broth, pepper, poultry seasoning, and salt, stirring until the sauce thickens, or about 5 minutes. Stir in milk, vegetables, and chicken cubes; cook for 3 minutes.
Divide mixture among six 1-cup ramekins, and top each with a biscuit. Carefully place ramekins and remaining biscuits on a baking pan.
Bake 15 to 18 minutes, or until biscuits are golden brown.