Pat the chicken dry with a paper towel. Season evenly on both sides with salt and pepper.
Put 2 tablespoons of the olive oil in a large, deep skillet (12-inches) and place over medium-high heat. When the oil starts to shimmer, add the chicken and cook without disturbing 6-8 minutes, or until it takes on a golden-brown color.
Flip the chicken over and add the onion and garlic to the pan, stirring to coat with the pan juices. Cook 2 or 3 minutes, until the onion softens.
Add the sauce, beans, rosemary and 1/2 teaspoon salt to the pan, scraping up any browned bits from the bottom of the pan. Cover and reduce the heat to medium-low. Cook 10 minutes.
Uncover the pan and continue to simmer 10 more minutes to thicken the sauce.
Drizzle the bread with olive oil and cut into 1/2-inch cubes.
Remove the chicken from the heat and stir in the kale until it wilts. Serve in shallow bowls topped with some of the bread and sprinkled with the cheese.
To prepare in a slow cooker: Follow steps 1-3 to sear the chicken, either on the stovetop or in your slow cooker insert if it's made for that. Add in the onion and garlic for the last 5 minutes. Transfer to the slow cooker with tomato sauce, beans and rosemary. Add another can of cannellini beans for a heartier texture, if you like. Cook on low for 5-6 hours or on high 4 hours. Stir in the kale and cheese and serve with the bread on top.