FOR THE GRAVY: Melt butter in medium saucepan over medium heat. Add onion and cook until softened, about 5 minutes. Stir in flour, garlic, sage, and paprika and cook, whisking constantly, until golden and fragrant, about 1 minute. Slowly whisk in broth and milk and bring to boil. Reduce heat to medium-low and simmer until thickened, about 10 minutes. Off heat, stir in Worcestershire sauce and season with salt and pepper to taste. Cover and set aside. (Gravy can be refrigerated for up to 2 days.).
FOR THE PORK: Meanwhile, combine flour, cornstarch, garlic powder, onion powder, 2 teaspoons pepper, 1 teaspoon salt, baking powder, and cayenne in bowl. Transfer 1 cup seasoned flour to shallow dish. Whisk 6 tablespoons milk and eggs together in second shallow dish. Stir remaining 2 tablespoons milk into remaining seasoned flour, rub with fingers until mixture resembles coarse meal, and transfer to third shallow dish.
Pat pork dry with paper towels and season with salt and pepper. Lightly score both uncut sides of pork pieces in ¼-inch crosshatch pattern. Working 1 piece at a time, coat pork lightly in seasoned flour. Place pork between 2 sheets plastic wrap and pound to ¼-inch thickness; remove plastic. Coat pork again with seasoned flour, dip into egg mixture, and dredge in milk and flour mixture, pressing firmly to adhere. Arrange pork on wire rack set inside rimmed baking sheet and refrigerate for 15 minutes or up to 4 hours.
Adjust oven rack to middle position and heat oven to 200 degrees. Warm gravy over medium-low heat, stirring occasionally. Heat oil in 12-inch skillet over medium heat until shimmering. Fry 2 pieces pork until deep golden brown and crisp, 2 to 3 minutes per side. Drain on clean wire rack set in rimmed baking sheet and place in oven. Fry remaining pork. Serve with gravy.