How to Make It
Fill a large saucepan with 1 inch of water and fit with a steamer basket. Bring the water to a boil. Place the broccoli and potatoes in the basket, cover, and steam until very tender, 10 to 12 minutes.
Drain the vegetables well and return them to the pot. Add the sour cream, butter, ½ teaspoon salt, and ¼ teaspoon pepper and mash to desired consistency.