Directions

1. Preheat oven to 450 degrees, with racks in upper and lower thirds. Brush a rimmed baking sheet with oil. In a small bowl, mix together 2 tablespoons mustard and ketchup.
2. In a medium bowl, combine beef, egg, panko, 1/2 cup cheddar, 1/2 teaspoon salt, and teaspoon pepper. Form into four 2-by-4-inch loaves; place on baking sheet. Brush with mustard mixture; top with remaining 1/2 cup cheddar. On another rimmed baking sheet, toss potatoes with 1 tablespoon oil; season with salt and pepper.
3. Transfer meatloaves to upper rack of oven, and place potatoes on lower rack. Bake until loaves are cooked through, 15 to 20 minutes, rotating sheets after 10 minutes. Remove loaves from oven; continue to roast potatoes until tender, about 5 minutes.
4. Meanwhile, in a large bowl, whisk together remaining tablespoon oil, remaining teaspoon mustard, and vinegar; season with salt and pepper. Add lettuce to bowl, and toss. Serve meatloaves with potatoes and salad.