Published November 1, 2007.
Adding carrots, parsnips, turnips, or celery root to mashed potatoes sounds like a good idea—until the mash turns out too watery, too sweet, and too bitter.
Most recipes for mashed potatoes and root vegetables give little forethought to the root vegetables, often consisting of mere footnotes instructing the cook to boil the chosen vegetable along with the potatoes. But as root vegetables and potatoes have different flavor profiles, starch levels, and water content, treating them the same way creates a bad mash.
Root vegetables like carrots, parsnips, turnips, and celery root can add an earthy, intriguing flavor to mashed potatoes. We wanted to make certain these stronger flavors didn't overwhelm the mild potatoes. And we needed to get the consistency right.
We found a 1-3 ratio of root vegetables to potatoes provided an optimal consistency, although the root vegetable flavor was barely recognizable. Sautéing them in butter separately from the potatoes worked well, but a two-burner, two-pot recipe was inconvenient. To use just one pot, we first sautéed the root vegetables in butter until caramelized and then added the potatoes with a little chicken broth. This gave us great flavor, but the mash had a gluey texture. The answer was to remove the starch from the potatoes by rinsing the peeled, sliced potatoes in several changes of water ahead of time. And since we were removing excess starch, we now had the option of using either Yukon Gold potatoes or starchier russets.
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