I just found this recipe after watching nearly all of the episodes.

INGREDIENTS

4 tablespoons unsalted butter, cut into 4 pieces
3 tablespoons heavy cream
1 teaspoon sugar
2 pounds sweet potatoes (2 large or 3 medium), peeled, quartered lengthwise, and cut into 1/4- inch-thick slices

INSTRUCTIONS

Combine butter, 2 tablespoons cream, 1/2 teaspoon salt, 1/4 teaspoon pepper, sugar, and sweet potatoes in large saucepan. Cooked, covered, over low heat until potatoes are fall-apart tender, 35-40 minutes.

Off heat, add remaining tablespoon cream and mash sweet potatoes with potato masher. Serve