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Roasted Garlic and Onion "Butter" Mashed Potatoes

Creamy and rich mashed potatoes, without butter, milk, or cream. But don't worry, you won't miss them at all!
Prep Time 30 mins
Cook Time 1 hr
Total Time 1 hr 30 mins
Course Side Dish
Cuisine American, Comfort Foods, Thanksgiving
Servings 8 servings + extra "butter" for next time


  • High Speed Blender
  • 9 x 13 Baking dish
  • Stock Pot
  • Collander
  • Strainer
  • Potato Masher
  • Chef's knife


  • 2 Yellow Onions Peeled and quartered
  • 1 Cup Garlic cloves Peeled, whole (try to find these in a bag in your produce section already peeled and just dump them in!)
  • 2-4 Sprigs Rosemary Fresh
  • 2-4 Sprigs Thyme Fresh
  • 4 Cups Vegetable Broth Heated, boxed or home made
  • 2 Cups Raw Cashews Soaked in water for at least 2 hours up to 24 hours
  • 8 Medium Russet Potatoes Peeled and cubed
  • 1/4 Cup Whole Fat Oat Milk Or any neutral flavored plant-based milk (optional)
  • 1 Tsp Sea Salt Or to taste
  • 1/2 Tsp Pepper Or to taste, freshly ground is best


  • Preheat oven to 400° F and prepare your ingredients
  • I like to measure everything out ahead of time so I'm not fumbling around and stressing myself out.
  • Place the onion, garlic, rosemary, thyme, salt, and pepper into a 9 x 13 glass baking dish and cover completely with the vegetable broth. Make sure the garlic is not exposed as it could easily burn and make the entire dish bitter.
  • Place the dish into the preheated oven uncovered, and set your timer for 30 minutes. At the 30 minute mark, stir and place them back into the oven. Continue braising until the liquid is reduced by more than half, checking frequently so the garlic does not burn but the onions began to carmelize (turn slightly brown on the edges).
  • Meanwhile, boil the potatoes in heavily salted water until they break apart easily with a fork (about 15-20 minutes). Drain and place in a large mixing or serving bowl and set aside.
  • Drain the soaked cashews, rinse under cold water, and place them into a high-speed blender. Don't blend them yet.
  • Note the aroma in your home and pretend it's Thanksgiving. Except it isn't. It's just Monday.
  • Remove the roasted vegetables and herbs from the oven. Remove the herbs from the mixture with tongs and discard. CAREFULLY ladle the remaining hot ingredients into the blender with the cashews, including the liquid. You may need to place a fine strainer over the blender to catch any stray stems from the herbs. Blend on high until it is completely smooth and creamy. Add more salt or pepper to taste. Lick the spoon and the spatula. Marvel at the deliciousness of this creation.
  • Transfer the mixture to a large serving bowl or storage bowl. This recipe makes much more "butter" than you need for your mashed potatoes, so think about how else you may want to use it...maybe spread it on a bagel? Or use it on a baked potato? Or use it in place of mayo on your favorite sandwich? Oh, how about a dollop over roasted asparagus? Omg...this on pasta. All the yesses.
  • Mash your boiled potatoes in the bowl and then add a generous ladle of the "butter" to the potatoes. Mash again. Taste. Are they flavorful and creamy? If not, continue adding the mixture and mashing until the potatoes are smooth and creamy and make you smile. Mashed potatoes are pure comfort food. It's okay to love this moment. You may add the optional plant-based milk at this step, depending on how thick your "butter" is and how you prefer your mashed potatoes.
  • Serve them alongside a tossed salad for a light meal or with your favorite protein and green veggie for a delicious and satisfying dinner. (Shown here with sweet and sour tofu and steamed brocolli).


If you want to wow your guests on Thanksgiving, serve these! No one will believe you that they are not slathered in butter and cream. 
I like to store the "butter" in small containers in the freezer and pull them out as I need them for baked potatoes, toast, bagels, over steamed broccoli...etc. This will keep in the fridge for 4-6 days or in the freezer for 6 months.
Potatoes do NOT freeze well, so only freeze the "butter." The mashed potatoes will keep in the fridge for 4-6 days. 
This recipe is adapted from Rouxbe.
Keyword Comfort, Easy, Healthy, Plant-based, Potatoes, Vegan