Ingredients

• 1 1/2 pounds rutabagas, peeled, cut into 1-inch pieces
• 3 pounds russet potatoes, peeled, cut into 2-inch pieces
• 6 tablespoons (3/4 stick) butter
• 3/4 cup (or more) buttermilk
• Chopped green onion tops or chives

Instructions

1. Cook rutabagas in large pot of boiling salted water until very tender, about 20 minutes. Using slotted spoon, transfer rutabagas to strainer. Press gently to release any excess liquid.
2. Add potatoes to same pot of boiling water; cook until tender, about 20 minutes. Drain well. Return potatoes and rutabagas to same pot. Add butter; mash well. Add 3/4 cup buttermilk; mash until smooth. Season with salt and pepper. (Can be made 6 hours ahead. Cover and chill. Stir over low heat to rewarm, adding more buttermilk by tablespoonfuls, if desired.)
3. Transfer potatoes to bowl. Sprinkle with green onions and serve.