Coat 13 x 9 x 2-inch baking dish with nonstick spray; set aside.

Heat oven to 250 degrees F. In a small bowl, stir 1 cup of the milk, 1 cup of the broth, polenta and salt. Bring remaining 1/2 cup milk and 1-1/4 cups of the chicken broth to a boil in a medium-size saucepan. Pour polenta mixture into saucepan of boiling milk mixture and whisk to combine. Cook for 2 minutes, stirring, or until thickened. Stir in Parmesan; spread into prepared dish. Cover and place in oven while preparing sausage and peppers. Spoon sausage mixture on top. Cut into squares and serve immediately.

In a small bowl, stir remaining 1 cup chicken broth, vinegar, cornstarch and sugar. Set aside.

Pierce sausages with a fork. Place in a large, deep skillet and cook over medium-high heat about 10 minutes, turning occasionally, until browned.

Add oil and onion to sausages, and cook 2 minutes, stirring occasionally.

Add peppers and cook for 4 minutes. Add garlic and cook for 30 seconds. Stir in vinegar mixture and bring to a boil. Cook for 1 minute, adding a little water if mixture appears too thick. Remove sausages and cut into 1/2-inch slices on the diagonal; return to pan.

Remove polenta from oven and spoon sausage mixture on top. Cut into squares and serve immediately.