Side Dishes

Buttermilk Mashed Potatoes with Roasted Garlic and Thyme

These mashed potatoes get a boost of fiber and nutty sweetness from rutabaga, while buttermilk and olive oil offer a heart-healthy alternative to the usual cream and butter.

By Yankee Magazine

Oct 22 2018


Buttermilk Mashed Potatoes with Roasted Garlic and Thyme

Photo Credit : Krissy O'Shea

There’s a secret ingredient in these potatoes: tender mashed rutabaga, which adds a wonderful nutty sweetness as well as extra fiber and antioxidants. We also replaced the usual cream and butter with buttermilk and olive oil, making this version a heart-healthy alternative to the typical mash.


8 servings


1 head garlic
2 tablespoons plus 1/4 cup olive oil
4 sprigs of fresh thyme
1 small rutabaga (about 1 1/2 pounds), peeled and cut into 1-inch cubes
6 Yukon gold potatoes (about 3 pounds), peeled and cut into 2-inch cubes
3/4 cup buttermilk at room temperature, plus more as needed
Salt and pepper, to taste


Preheat oven to 400° and set a rack to the middle position. Remove any papery skin from the garlic, then cut off the top third of the head, exposing the cloves. Place garlic on a piece of foil, drizzle with 2 tablespoons oil, then wrap up the foil to create a packet. Bake until very tender, 40 to 45 minutes. Remove from oven and set aside.

In a small saucepan over low heat, add the remaining ¼ cup olive oil and the thyme. Bring to a gentle simmer and cook for five minutes. Remove from heat and let stand.

Set one medium and one large pot of salted water over high heat and bring to a boil. Add the rutabaga to the medium pot, reduce heat to a simmer, and cook until very tender, about 25 minutes. Add the potato to the large pot and simmer until tender, about 15 minutes.

Once the rutabaga is soft, drain and return to the pot. Using a hand blender or electric mixer, purée the rutabaga until smooth. Add six cloves of roasted garlic to the rutabaga and purée again. (Save any additional cloves for dressings or to spread on toast.) 

Once the potatoes have finished cooking, drain them and add them to the mashed rutabaga. Add ¾ cup buttermilk, and mash by hand until smooth. Remove thyme sprigs from the warm olive oil and drizzle oil over the potato mixture, then stir to combine. For a thinner mixture, add more buttermilk. Season with salt and pepper to taste. Serve immediately, or cover and place in a 200° oven to keep warm until ready to serve.