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Sweet Onion and Root Vegetable Gratin

Sweet Onion and Root Vegetable Gratin / Gail Ingram Photography

  “You eat potatoes!?” a friend of mine asked shockingly after I told her potatoes were one of the ingredients in the sweet onion and root vegetable gratin recipe I was making for dinner. “Why would I not eat potatoes?” I asked. “Because they are a refined carb” my friend answered. Ummm. No, that’s not really true. Potatoes are not refined; in fact, they are the perfect example of a “whole food” carbohydrate. A refined carbohydrate would be something like white flour—white flour begins as a healthy whole grain wheat kernel and then, during “refinement” is stripped of its nutrient-dense germ and fiber-rich bran. Potatoes are just potatoes, exactly what you find in nature…as is. Potatoes are a perfectly fine root vegetable to eat. And they taste good too.

Potatoes are Not Empty Carbs

Potatoes are always satisfying, apples of the earth, or pommes de terre, or at least that’s what they say in France. But somehow the low-fat power-food of the fitness-crazed 80’s era, have come under increased scrutiny by fitness, health and weight loss experts in the last decade or so. Like legwarmers, potatoes have become very unfashionable among the health-fad enthusiasts. Let’s try to set the potato record straight… First, potatoes are not empty calories. If you eat potatoes “whole” —with their skins on the way you should eat them— they are a nutrient-dense food filled with fiber, vitamin C, iron, B-vitamins, antioxidants, phytonutrients and even potassium (almost double the amount of potassium per serving than bananas.) In fact, potatoes meet FDA requirements for the health claim, “consuming foods such as potatoes that are good sources of potassium and low in sodium may reduce the risk of high blood pressure and stroke.” Potassium is a mineral that is part of every cell in your body. It helps regulate fluid and mineral balance and in doing so helps maintain normal blood pressure. Potassium is also vital for transmitting nerve impulses and helping muscles contract. So there’s good stuff in potatoes for sure.

But are Potatoes Fattening?

But what about being fattening? Will eating potatoes burst your pants button? Are potatoes fattening? Nope. Not if you can keep from piling on the sour cream, butter, bacon bits and other fatty fixings. Potatoes are not fattening because they are not empty calories.  Plus, they are an excellent source of resistant starch so you don’t even absorb all of the starch calories in the potatoes you eat. Resistant starch is as close to a “miracle” starch as it gets. Considered a functional fiber, resistant starch actually resists digestion, meaning the calories in resistance starch cannot be stored as fat. Considered the third type of dietary fiber, resistant starch can deliver some of the benefits of insoluble fiber and some of the benefits of soluble fiber. And, because resistant starch skips digestion you end up with lower blood sugar and insulin levels—and better ability to burn fat–following a resistant starch-rich meal. Studies show a diet rich in resistant starch not only helps control blood sugar levels and reduce fat storage after meals, but also helps you feel more full, so you eat less. (1) And potatoes are an excellent source of resistant starch. Another reason potatoes (with their skins!) are so satisfying is because they are a high volume food that can stretch your stomach. This process stimulates your digestive system’s distension nerves sending the message to your brain that you are feeling full. Your hunger is then quieted and you feel satisfied. Once you get over your fear of potatoes you can enjoy the recipe for my sweet onion and root vegetable gratin, just be sure to keep the skins on your potatoes —it will speed up prep time, boost fiber and help give the dish a great rustic texture. Print

Sweet Onion and Root Vegetable Gratin

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  • Yield: 6 1x


  • 2 tablespoons extra virgin olive oil
  • 6 cloves garlic, crushed
  • 1 large sweet onion, such as Vidalia, thinly sliced
  • Unrefined sea salt, to taste (such as Real Salt)
  • White pepper, to taste
  • 1 ¼ pounds Yukon Gold potatoes or fingerling potatoes
  • 2 parsnips, peeled and cut
  • 3 turnips, peeled and cut into chunks
  • ½ cup organic vegetable broth
  • ½ cup cashews
  • 1 teaspoon fresh thyme
  • Paprika, to taste
  • ½ cup grated Gruyere cheese (optional)


  1. Heat extra virgin olive oil in a large heavy skillet over medium-high heat. Add garlic and sauté 30 seconds. Add onions, season with salt and pepper to taste and cook until very soft, about 15 minutes.
  2. While onions cook place potatoes, parsnips and turnips in a large pot and cover with water. Add salt and bring to a boil. Cook until vegetables are tender, about 12 to 15 minutes. Drain and return vegetables to pot.
  3. Place the vegetable broth, cashews and thyme in a blender and process until smooth and creamy.
  4. Add the cashew cream a little at a time to the pot with the potatoes, parsnips and turnips. Use a potato masher to mash the potatoes (or a handheld stick blender for an ultra-creamy texture.)
  5. Preheat broiler. Transfer the mashed vegetables to an 8 x 8-inch casserole or individual gratin dishes. Sprinkle on a bit of paprika and top with onions and Gruyere cheese (optional). Brown gratin under hot broiler until bubbly, about 3 minutes. Serve warm.

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Note: To make this vegan simply eliminate the cheese (and yes, it still tastes delish, even without the cheese!)

© 2024 clean cuisine Recipe by:


Ivy Larson

In 2010, Clean Cuisine was launched because Ivy Larson wanted to share her anti-inflammatory lifestyle and delicious recipes using ingredients in their most natural and nutrient-rich state. In 2020, Ivy passed the website to Aimee and Madison. Since then, they have been adding new recipes and nutrition posts while updating old recipes and articles. Thanks for visiting Clean Cuisine!

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Saturday 6th of January 2018

Hi Ivy,

Thanks for the recipe . Looking forward to adding a healthy spin to traditional mashed potatoes ?. Do I peel the potatoes?

Ivy Larson

Wednesday 10th of January 2018

Hi Kaneez! No, no need to peel the potatoes ;) Please let me know how it turns out for you!

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