In a small bowl, combine 1 cup soy milk and vinegar and let sit 5 minutes or until it looks lumpy and thick. In a large shallow bowl, stir together flour, 2 teaspoons salt, onion powder, cayenne powder and pepper and set aside. In a large Ziploc bag pour soy milk mixture over chicken and let sit 30 minutes, refrigerated.

Place potatoes in a large pot and cover with water. Bring to a boil over medium high heat and reduce to a simmer. Cook 20 to 25 minutes or until fork tender. Drain well and return to pot. Using a potato masher or ricer, mash potatoes until smooth but leaving a few lumps. Stir in remaining soy milk, vegan butter, remaining 2 teaspoons salt and pepper and set aside, covered to keep warm.

Heat oil in a 12-inch heavy cast iron skillet over medium high heat. Take one piece of chicken out of the Ziploc and dip in flour mixture, rolling around to coat well. Shake off excess before carefully putting in the oil and repeat with remaining pieces. Fry over medium to medium high heat for 6 to 8 minutes on each side. Continue frying and turning 2 to 4 minutes or until chicken is golden and brown on all sides. Remove from oil and drain on paper towels.

Prepare Best Ever Gravy according to recipe instructions and serve over mashed potatoes.