Preheat oven to 450°F. Place potatoes and onion in a rimmed baking sheet. Drizzle with 1 tablespoon olive oil, and sprinkle with 1/2 teaspoon each salt and pepper. Bake in preheated oven until potatoes are golden brown and tender and onions are soft, about 25 minutes.
Meanwhile, stir together 1/3 cup flour and 1/2 teaspoon each salt and pepper in a small, shallow dish. Dredge pork chops in flour mixture, evenly coating all sides. Heat remaining 2 tablespoons olive oil in a large skillet over medium-high. Add pork chops, and cook until golden, about 4 minutes per side. Transfer pork chops to a platter.
Melt 2 tablespoons of the butter in skillet. Add 1 tablespoon of the flour, whisking until smooth. Add wine, and cook, stirring and scraping to loosen browned bits from bottom of skillet, until reduced by about one-third, about 2 minutes. Add chicken stock; bring to a boil, and reduce heat to medium-low. Cook, stirring occasionally, until sauce is thickened, about 4 minutes.
Cook peas according to package directions; transfer to a bowl. Stir in remaining 1/2 teaspoon salt, 1/4 teaspoon pepper, and 1 tablespoon butter until combined. Serve pork chops with potato mixture, peas, and sauce; sprinkle with parsley just before serving.