Place chicken and 2 cups of the buttermilk in a large bowl, cover, and refrigerate for at least 2 hours or overnight.

Preheat oven to 425 degrees, and spray a large wire rack with nonfat cooking spray. Place the rack over a large baking dish or baking sheet.

Remove chicken from buttermilk. Pat dry a bit with paper towels and then season the chicken with salt and pepper.

In a large Ziploc bag, combine 1/2 cup flour, onion powder, garlic powder, and paprika. Shake well to mix. Place chicken pieces in a bag and shake well until all pieces of chicken are evenly coated.

Place liquid egg substitute in one bowl and the Panko, thyme, and salt & pepper in another bowl. Dip each piece of chicken in egg, shake off excess, then dip into Panko and turn to coat well.

Arrange the chicken pieces on the wire rack and place them in the oven. Cook for 15 minutes then, lower the heat to 375 degrees, and cook for another 20 to 25 minutes, or until cooked through and crispy.

While chicken is cooking, make the country gravy by melting butter in a medium-sized saucepan over medium-high heat. Whisk in flour, and cook for about another minute. Slowly whisk in the remaining 1 1/2 cups buttermilk,1/2 cup of the broth, and the poultry seasoning, whisking constantly and blending the liquid with the flour mixture until combined. Let the gravy come to a boil and then reduce heat and simmer until the gravy thickens up. If the mixture thickens too much, add more broth as needed until the gravy is the consistency that you want.

Serve each chicken fillet, topped with about 1/3 cup of the country gravy.