▢ 1.5 pounds potatoes (Russet, Yukon, Red Potatoes), peeled and cut into 1-inch chunks  ▢ 8 ounces curly kale, roughly chopped  ▢ 4 tablespoons unsalted butter and more for serving  ▢ 1/2 cup heavy cream, room temperature  ▢ 1/2 teaspoon salt  ▢ freshly ground pepper