Any small round white or red potato, or any of the fingerling varieties, works well for this dish. If you use large potatoes, cut them into bite-size pieces.
Place potatoes in a medium saucepan, and cover with water. Bring to a boil over high heat; add salt. Reduce heat slightly, and simmer until tender, 10 to 12 minutes. Drain in a colander. Transfer to a medium bowl, and cover loosely.
Place a steamer basket in a medium pot with about 2 inches of water. Steam beans and peas until tender, 5 to 6 minutes. Remove; add to cooked potatoes.
Combine the cream and butter in a small saucepan, and bring to a boil over medium-high heat. Reduce heat to medium, and gently boil until slightly thickened, 5 to 6 minutes. Pour cream over vegetables, and season with salt and pepper. Toss to combine.