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+ servings
tri-color sweet potatoes spiraled in cast iron with baked cream sauce

Savory Rainbow Sweet Potatoes Au Gratin

This Savory Rainbow Sweet Potatoes au Gratin with cheddar rosemary sauce proves that sweet potatoes don't always have to be covered in brown sugar & pecans. 

Course Side Dish
Cuisine American
Keyword au gratin, Side Dish, sweet potatoes
Prep Time 20 minutes
Cook Time 1 hour 30 minutes
Total Time 1 hour 50 minutes
Servings 8
Calories 367 kcal
Author Christie Vanover


  • 1 white sweet potato
  • 1 yellow sweet potato (yam)
  • 1 purple sweet potato
  • 3 tbsp flour
  • 3 tbsp butter
  • 1 tsp fresh rosemary minced
  • 1/2 tsp kosher salt
  • 1/2 tsp fresh ground black pepper
  • pinch nutmeg
  • 1 cup heavy cream
  • 1 cup milk
  • 1 cup white cheddar cheese shredded


  1. Heat oven or smoker to 400F degrees. 

  2. Slice each potato into 1/8-inch slices.

  3. Stack the potatoes into 2-3-inch stacks, alternating potato colors.

  4. Grease a round baking dish or cast iron pan. 

  5. Transfer the potato stacks to the pan, laying them on their sides and creating an outer and inner circle. 

  6. In a sauce pot, melt the butter over medium heat. Whisk in the flour. Cook for three minutes, whisking occasionally. Add the rosemary, salt, pepper and nutmeg.

  7. Whisk in the cream and milk. Continue whisking, until it starts to thicken. 

  8. Remove the pan from the heat, and whisk in the cheese. 

  9. Pour the sauce over the potatoes. Cover with foil, and place on a sheet pan. 

  10. Bake in a 400F-degree oven or smoker for one hour. Remove the foil, and bake 20-30 more minutes, or until the cheese begins to brown and bubble. 


This recipe was inspired by Salt N Copper's recipe for Potatoes Au Gratin with Shallots, Thyme, and Gruyere

Nutrition Facts
Savory Rainbow Sweet Potatoes Au Gratin
Amount Per Serving
Calories 367 Calories from Fat 189
% Daily Value*
Fat 21g32%
Saturated Fat 13g81%
Cholesterol 70mg23%
Sodium 314mg14%
Potassium 998mg29%
Carbohydrates 37g12%
Fiber 4g17%
Sugar 3g3%
Protein 7g14%
Vitamin A 3210IU64%
Vitamin C 18.8mg23%
Calcium 180mg18%
Iron 0.9mg5%
* Percent Daily Values are based on a 2000 calorie diet.