Cook kale in a pot of boiling salted water (1 1/2 tablespoons salt for 4 quarts water), uncovered, until tender, about 7 minutes. Drain kale, then immediately transfer to an ice bath to stop cooking. When kale is cool, drain but do not squeeze.
While kale cooks, peel potatoes and cut into 1/2-inch pieces. Simmer in cream with 1/2 teaspoon salt and 1/4 teaspoon pepper in a heavy medium saucepan, covered, stirring occasionally, until tender, 15 to 20 minutes.
Purée potato mixture with kale in 2 batches in a food processor until just smooth (use caution when blending hot liquids). Transfer to a 4-to 5-quart heavy saucepan and cook over low heat, stirring frequently, until heated through. Season with salt and pepper.
Gourmet,December 2008, by Ruth Cousineau