Purple Sweet Potato Soup with Roasted Cauliflower and Tarragon

I have a potato obsession. But my favorite potato is the mighty sweet potato. Unlike a regular potato, a nightshade family member, the sweet potato is a large edible root within the morning glory family. And sweet potatoes come in many colors too!

While potatoes with orange flesh are the richest in beta-carotene. Sweet potatoes with purple flesh are richer in anthocyanins. Beta-carotene and anthocyanins are naturally occurring plant “Phyto” chemicals that give vegetables their bright colors. Phytochemicals are biologically active compounds found in plants and are known to:

  • Aid the function of the immune system.
  • Protect cells and DNA from damage that may lead to cancer.
  • Reduce inflammation.
  • Slow the growth rate of some cancer cells.
  • Help regulate hormones.

Why use a purple potato? Because anthocyanins have the capacity to lower blood pressure, improve visual acuity, reduce cancer cell proliferation, inhibit tumor formation, prevent diabetes, and lower the risk of CVD, which modulates cognitive and motor function.

This pretty warm winter soup was inspired by another anthocyanin…the açaí bowl!. It’s super healthy comes together very quickly. You can easily make this a “no-oil” soup by steaming your vegetables instead of roasting them. 

If you choose to use oil, be sure to keep the temperature well below the oil’s smoke point or the point at which the oil starts to burn (that’s about 410 degrees for extra virgin or unrefined olive oil). Because overheating oil breaks down the nutritional composition of the oil changes the flavor, and releases harmful free radicals. 

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Purple Sweet Potato Soup with Roasted Cauliflower and Tarragon

  • Author: Stephanie Bosch


I added a delicious beet puree to this soup, but you can add whatever you want.  Good choices might be pieces of roasted cauliflower, pumpkins seeds, hemp seeds, or soy cream. 


  • 3 large purple sweet potatoes, peeled and medium diced
  • 1 large head of organic cauliflower, chopped into medium florets
  • 2 large leeks, white part only, thinly sliced
  • 2 cloves garlic, mined
  • 2 tablespoon olive oil
  • 1 teaspoon dried thyme
  • 1 teaspoon dried tarragon
  • 2 tablespoons fresh tarragon
  • 1 (32 oz) container organic vegetable stock
  • salt and pepper to taste


  1. Preheat oven to 400°.
  2. Add chopped potatoes and cauliflower to a mixing bowl and toss with 1 tablespoon of olive oil. 
  3. Add spices to a small bowl and mix well. 
  4. Spread vegetables evenly on a parchment-lined baking sheet. 
  5. Sprinkle the spice mix over vegetables. Place baking sheet in the oven, and roast vegetable for 30 minutes, turning vegetables at the half-way mark. 
  6. When vegetables are done, remove from oven and let cool. 
  7. Warm a dutch oven over medium heat. When the pan is heated, add oil. When oil begins to shimmer, add the leeks and saute until leeks have softened and are slightly brown. 
  8. Add garlic and sauté until fragrant, about 30 seconds to a minute. 
  9. Add cooled vegetables and vegetable stock to a dutch oven, and stir. 
  10. When the soup is warmed, use an immersion blender, or carefully ladle half of the soup mixture into a blender. (If using a high-speed blender, be careful to hold the lid, as the heat can build pressure and the lid can fly off). Continue until all the soup is blended to the consistency you prefer. **I blended the first batch until entirely smooth. For the second batch, I blended it to have some texture and then mixed the two. 
  11. Return to dutch oven and taste for seasoning. 
  12. Serve warm and top with fresh tarragon, roasted cauliflower, hemp seeds, pumpkins seeds (pepita’s), or beet puree. 


**While blending the soup, I placed the first pureed batch into a large mixing bowl.  

2 thoughts on “Purple Sweet Potato Soup with Roasted Cauliflower and Tarragon

    1. Yes! You can use shallots (about 3) or you can just use an onion! Three leeks is the equivalent of one large onion.

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