• Spray inside of 4- to 5-quart slow cooker with cooking spray. In 12-inch nonstick skillet, heat 1/4 cup butter over medium-high heat. Add onions, 1 tablespoon thyme, 1/2 teaspoon of the salt and 1/4 teaspoon of the pepper; cook 10 to 15 minutes, stirring occasionally, until onions start to soften.

Reduce heat to medium; cook 8 to 10 minutes, stirring frequently, until onions are starting to brown. Add chicken broth; heat to simmering. Remove from skillet to medium bowl.

Season chicken breasts with remaining 1/2 teaspoon salt and 1/4 teaspoon pepper; add chicken, skin-side down, to skillet. Cook over medium-high heat 2 to 3 minutes on each side or until browned. Transfer to slow cooker; top chicken pieces with onion mixture. Cover and cook on Low heat setting 3 to 3 1/2 hours or until juice of chicken is clear when thickest parts are cut to bone (at least 165°F).

Remove chicken from slow cooker to serving platter; cover and keep warm. In small bowl, mix cornstarch and cold water with whisk; beat into onion mixture in slow cooker. Cover; cook on High heat setting 10 to 15 minutes or until bubbly and slightly thickened. Top chicken with sauce.

Meanwhile, heat oven to 375°F. In small microwavable bowl, microwave 2 tablespoons butter and the garlic powder uncovered on High 20 to 30 seconds or until melted. Brush butter mixture on both sides of bread. Arrange on 15x10x1-inch pan; top each slice with 1 tablespoon of the shredded cheese. Bake 3 to 5 minutes or until cheese is melted and bread is slightly toasted; remove from oven.

Serve chicken with toasted bread. Garnish chicken with additional thyme or parsley.