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Caramelized Onion and Sweet Potato Quiche

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Makes 6 servings


Prep Time

15 minutes


Cook Time

90 minutes

kikkoman products used:


1 frozen pie pastry shell, thawed
2 teaspoons Kikkoman® Sesame Oil
1 red onion, sliced
1 ½ tablespoons Kikkoman® Soy Sauce
¼ of a sweet potato, sliced thinly with a mandolin
3 handfuls of fresh spinach
4 eggs
½ cup milk


  1. Bake your pie shell according to the directions on the package.
    If you’re using a pastry in your own pie plate: roll out the dough and place into a pie plate, making sure to trim off the edges. Use pie weights to make sure that the crust cooks without bubbling up. Once finished, remove from the oven and allow to cool.
  2. In a pan, heat sesame oil to medium heat and add the onions. After 15 minutes, add in 1 tablespoon of soy sauce and lower the heat. Cook for an additional 20-25 minutes. Your onions are done when they are soft, sweet, and caramel colored.
  3. Remove onions from pan and set aside.
  4. Preheat your oven to 400°F.
  5. Place the sweet potato into the pan on medium heat and allow to sauté for 5-10 minutes or until they are soft and pliable. Remove the sweet potato from the pan and set aside.
  6. Add spinach to the pan on low heat, stirring constantly until the spinach has wilted.
  7. Place spinach, sweet potato, and onion into your cooked pie shell, making sure to spread the mixture evenly.
  8. In a bowl, whisk together eggs, milk, and ½ tablespoon of soy sauce. Pour egg mixture gently into the pie shell, without allowing the egg mixture to spill over the pastry edge.
  9. Place the quiche into the oven for 30-40 minutes or until you can insert a knife into the center of the quiche and it comes out clean.
  10. Allow to rest for 5 minute and serve!


Even people who love soy sauce and use it all the time are often surprised to learn what it is and how it’s made. We make ours from just four simple ingredients—water, soybeans, wheat, and salt. Those ingredients are transformed through a traditional brewing process—much like making wine or beer—that has remained unchanged for centuries.


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