Bloody Mary Chicken Crockpot

4 boneless, skinless chicken breast halves
1/2 stick butter
1 small red onion, finely chopped
1/8 cup flour
14 1/2 ounce can Hunt's Diced Tomatoes with Roasted Garlic(OR can tomatoes and minced Garlic)
1/4 cup brown sugar
1/4 cup dried celery or 2 ribs fresh celery, chopped
1 tablespoon A-1® Steak Sauce
1 liter Major Peters All Natural Bloody Mary Mix

Trim all visible fat from the chicken breasts. Saute the chicken breasts in 2 tablespoons of the butter. When golden brown, remove them to the crockpot. Add the rest of the butter to the skillet and saute the onions and cook them until clear and getting tender. Sprinkle the flour over the butter and onion mix to form a paste, then add the tomatoes, brown sugar, A-1, celery, and the bloody mary mix. When hot, pour the sauce over the chicken breasts in the crockpot. Cover the crockpot and cook on low for 8 hours.