Season chicken with salt and pepper. Heat olive oil in a skillet and brown chicken for a couple of minutes on both sides. You may have to do this in batches.
Place chicken in the slow cooker and sprinkle with the Italian seasoning, onion powder, and chicken bouillon. Add the chicken broth, butter, lemon zest and lemon juice. Put lid on and cook on low heat for 4 hours or high heat for 2 hours.
Remove chicken and set onto serving platter. Heat reserved juice from slow cooker in a saucepan. In a bowl, stir 2 tablespoons of cornstarch with 1/4 cup of milk. Add to the saucepan and add the remaining 3/4 cup of milk as well. Stir until the sauce begins to thicken. Pour over the chicken and sprinkle with parsley and Parmesan cheese.
Note: Metric ingredient measurements are provided as a courtesy using a third-party calculator and are rounded to the nearest unit. The recipes provided on this site have not been tested with metric measurements and their accuracy cannot be verified.
The nutritional information provided is based on third-party calculations and is an estimate only. Accurate nutritional facts will vary based on the particular brands used, portion sizes, measurement accuracy and more.