Spread the bread crumbs across the bottom of a large dry skillet and bring over medium heat. Cook for a few minutes, stirring every minute or so to rotate which crumbs are on the bottom until the crumbs are browned.

Combine the flour and chicken breasts in a large Ziploc bag and seal shut. Shake until the breasts are coated with the flour.

In a shallow bowl, lightly beat the 2 egg whites. Place the bread crumbs on a separate shallow bowl or plate. Dip one floured chicken breast in the egg whites, coating all sides, and then press it into the bread crumbs. Flip the breast to coat with crumbs and then place it into your slow cooker. Repeat with three remaining breasts, creating a single layer of breaded chicken breasts at the bottom of your slow cooker.

Spread the marinara sauce over the top of the chicken layer. Place the lid on your slow cooker and cook on low for 5-6 hours. About 15-20 minutes before the cooking is finished, add the cheese so it can melt. Serve and enjoy!