1 cup (2 sticks) clarified butter*
2 pounds white boiling potatoes, peeled, very thinly sliced
1 pound sweet potatoes, peeled, very thinly sliced
1 pound red-skinned potatoes, very thinly sliced
1 tablespoon chopped fresh oregano
1 tablespoon chopped fresh thyme
Preheat oven to 450 degrees. Drizzle 2 tablespoons clarified butter into bottom of 10-inch-diameter ovenproof skillet with 2-inch high sides. Swirl skillet to coat bottom. Placing all potatoes between layers of paper towels, dry well. Arrange half of white potatoes in overlapping circular pattern in prepared skillet. Season with salt and pepper. Drizzle with 2 tablespoons clarified butter. Arrange half of sweet potatoes in overlapping circular pattern over white potatoes. Season with salt and pepper. Drizzle with 2 tablespoon clarified butter. Repeat with red-skinned potatoes, adding salt, pepper and 2 tablespoons butter. Repeat with remaining white potatoes, seasoning and adding butter. Cover with foil.
Bake potatoes 25 mintues. Uncover and bake until potatoes are tender and top is golden, about 1 hour 15 minutes. Run sharp knife around edge of potatoes. Turn out onto cake onto platter. Sprinkle with herbs and cut into wedges.
*To clarify butter, melt butter in saucepan. Remove all milk solids from the top of the melted butter.
