Ingredients

• 1 pound Yukon gold potatoes (about 3)
• 1 pound sweet potatoes (about 2)
• Kosher salt
• 6 tablespoons unsalted butter, diced
• 1/3 cup heavy cream, warmed
• 1/3 cup sour cream
• Freshly ground black pepper
• 1 tablespoon packed light brown sugar
• Pinch of cayenne pepper

Instructions

1. Put the potatoes and sweet potatoes in a large saucepan and cover with cold water by 1 inch. Add a generous pinch of salt, bring to a simmer and cook until the potatoes are easily pierced with a knife, 35 to 40 minutes. Drain and let cool slightly. Peel the Yukon gold potatoes and transfer to a medium bowl. Peel the sweet potatoes and transfer to a separate bowl.
2. Divide the butter between the 2 bowls. Add the heavy cream and sour cream to the Yukon gold potatoes and mash well with a potato masher; season with salt and black pepper. Add the brown sugar and cayenne to the bowl with the sweet potatoes and mash well; season with salt and black pepper.
3. Dollop the potatoes and sweet potatoes into a warmed serving dish and swirl using a large spoon. (The potatoes can be made up to 2 hours ahead; set aside in a baking dish. Reheat, covered, at 350 degrees F, 15 to 20 minutes.)
4. Photograph by Chris Court