Makes 6 servings.
• 5 tablespoons unsalted butter, melted, divided, plus more for greasing the pan
• 6 medium russet or Yukon Gold potatoes (about 1 1/2 pounds total)
• 2 teaspoons M5 Spice Rub
• 2 tablespoons chopped fresh flat-leaf parsley leaves, for garnish
• Sour cream, for serving
Preheat the oven to 425 degrees F. Grease a 12-inch cast-iron pan with butter or bacon fat.
Cut each potato crosswise into 1/8-inch-thick slices without cutting all the way through to the bottom – leave about 1/4 inch of the potato intact (this will help hold them together). A good trick is to lay two chopsticks on either side of the potato to keep the knife from going all the way through. Arrange the potatoes in the pan with about an inch in between.
Brush the potatoes all over with half of the butter. Sprinkle evenly with 1 teaspoon of the spice rub. Cover the pan with aluminum foil and bake for 30 minutes.
Remove the foil and drizzle the potatoes, which should have opened up slightly, with the remaining butter and the remaining 1 teaspoon spice rub. Bake uncovered until the potatoes are crispy on the edges and soft in the center, about 15 minutes longer. Garnish with the parsley, then serve with sour cream.