Place pork, one piece at a time, between two sheets of parchment paper or wax paper then pound cutlets carefully but firmly until approximately ¼" thick. Repeat process with all cutlets.
Put ⅓ cup cornstarch into a pie dish or bowl and set aside. Pour buttermilk into a second pie dish or bowl then whisk in dry mustard, paprika, garlic powder, salt and pepper. On a separate plate, add ⅓ cup cornstarch and panko breadcrumbs then toss until well combined.
In a large skillet, add enough oil to come ¼" up the sides of the pan. Heat over medium-high heat, making certain to keep an eye on it while you bread the cutlets.
While the oil is heating up, line up the plates so that the cornstarch is first, then buttermilk and the breadcrumb mixture is last. In a three-step process, with your left hand, dredge one cutlet in cornstarch then shake off any excess. Next, with your right hand, drop it into the buttermilk mixture to coat completely then cover cutlet with the breadcrumb-cornstarch mixture. Transfer breaded pork to a wire rack over a baking sheet then repeat with the next two cutlets. This will give you a clean dry hand to work with.
Now place the three cutlets so that they fit comfortably into the hot skillet and let them cook 4–5 minutes while you bread the rest of the cutlets or until light golden brown. It’s very important not to overcrowd the pan or the cutlets won’t get crispy—this is why you work in batches.
Carefully flip cutlets over then cook an additional 4–5 minutes until golden brown on the second side and pork is cooked through. Cover paper towels over the wire rack that you used during the dredging process. This will keep you from having to wash another plate. Transfer the cooked cutlets to the paper towel-lined rack to drain and let rest 4–5 minutes before serving.
Add more oil to the pan and bring it up to temperature. Repeat process with the remaining three cutlets. Serve with mashed potatoes and gravy! Yum-yum!