Preparation

• In a small bowl, whisk the mayonnaise, garlic, and paprika. Set aside.
• In a medium bowl, whisk the buttermilk, egg, 1-1/2 tsp. salt, 1/2 tsp. pepper, and cayenne. Add the steak, turn to coat, and marinate, covered, at room temperature.
• Position a rack in the upper third of the oven, and heat the oven to 450°F. Toss the potatoes on a large rimmed baking sheet with 2 Tbs. of the oil, 1/2 tsp. salt, and 1/4 tsp. pepper, and arrange in a single layer. Roast until the potatoes begin to brown, about 15 minutes. Turn with a spatula, and continue roasting until browned and crisp, 15 to 20 minutes more.
• Meanwhile, prepare the steak. Pour the breadcrumbs into a wide shallow bowl, and have a large platter on hand. With a fork, lift two to three pieces of steak from the buttermilk mixture, and drop into the breadcrumbs. Press the breadcrumbs on all sides, and transfer to the platter. Repeat with the remaining steak pieces.
• Pour the remaining 4 Tbs. oil into a cast-iron skillet. Heat the oil over medium heat until shimmering, about 3 minutes. Cook the steak in a single layer in batches until golden-brown all over, about 2 minutes per side. Add more oil as needed. Serve the steak and fries with the aïoli for dipping.