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Kabocha Gratin
4.9 from 56 votes

Kabocha Gratin

Kabocha Gratin combines sweet kabocha squash with mushrooms, onions, and a creamy white sauce, topped with gruyere cheese and breadcrumbs for a golden crust. The dish balances earthy mushroom flavors with the richness of the sauce and the natural sweetness of the squash, making it a comforting baked casserole suitable as a side or vegetarian main, with optional macaroni to add heartiness.

Prep Time
30 mins
Cook Time
45 mins
Total Time
1 hr 15 mins
Servings: 8 individual
Calories: 367 kcal
Course: Side Dish, Main Course
Cuisine: Japanese

Ingredients

  • 1½ lb kabocha squash (½ kabocha)
  • 1 clove garlic
  • ½ onion (4 oz, 114 g)
  • 9.5 oz king oyster mushrooms 1 package, eringi
  • 3.5 oz shimeji mushrooms (1 package)
  • 1½ Tbsp extra virgin olive oil
  • 1½ Tbsp miso paste
  • 1 cup water
  • kosher salt Diamond Crystal brand
  • black pepper freshly ground
  • 1 Tbsp butter to grease the baking dishes, unsalted
  • ½ cup gruyere cheese (freshly grated)
  • ¼ cup breadcrumbs 4 Tbsp, Japanese style panko
For the Macaroni (optional)
  • 2 Tbsp kosher salt Diamond Crystal brand
  • 1½ cups elbow macaroni 6 oz; makes 3 cups cooked macaroni, uncooked
For the White Sauce
  • 4 Tbsp butter unsalted
  • ½ cup all-purpose flour
  • 3⅓ cups milk warm, whole
  • kosher salt to taste, Diamond Crystal brand
  • ⅛ tsp white pepper to taste; or substitute freshly ground black pepper, powder
  • ¼ tsp nutmeg to taste; optional, freshly grated
For the Garnish
  • chives minced, or parsley

Instructions

    Cup of Yum
  1. Microwave 1½ lb kabocha squash for 2 minutes and remove the seeds and pith; learn how to cut it open in my post about kabocha squash.
  2. Cut into wedges and remove the skin.
  3. Cut into small chunks, about 1-inch (2.5-cm) cubes.
  4. Thinly slice ½ onion and 1 clove garlic.
  5. Discard the bottom of 3.5 oz shimeji mushrooms. Separate the shimeji mushrooms into small pieces with your hands.
  6. Cut 9.5 oz king oyster mushrooms (eringi) into 2-inch (5-cm) pieces and slice thinly.
To Make the White Sauce
  1. In a large saucepan, melt 4 Tbsp unsalted butter over low heat. Once the butter is completely melted, add ½ cup all-purpose flour (plain flour) and mix well until blended. Cook the flour, stirring constantly, without browning, for 1–2 minutes.
  2. Gradually add in 3⅓ cups whole milk, ½ cup at a time, while stirring constantly until the sauce is completely smooth and without any lumps.
  3. Season with a pinch of Diamond Crystal kosher salt, ⅛ tsp white pepper powder (or freshly ground black pepper), and ¼ tsp freshly grated nutmeg.
  4. Cook the white sauce, stirring constantly until the sauce has thickened, about 10–15 minutes. It should be a thick, creamy sauce. Taste the sauce one more time and adjust the seasonings to make sure it’s not bland. Set aside. Tip: If you end up with leftover white sauce, it can be stored in an airtight container in the refrigerator for up to 3–4 days.
To Cook the Kabocha
  1. In a large frying pan, heat 1½ Tbsp extra virgin olive oil. Add the garlic and onion and sauté until the onion is coated with oil.
  2. Add the oyster and shimeji mushrooms and cook for 2–3 minutes.
  3. Once the mushrooms are tender, add 1½ Tbsp miso and mix well together.
  4. Add the kabocha and 1 cup water for steaming. Close the lid and cook kabocha on medium-low heat until it’s tender, about 10 minutes.
To Cook the Macaroni (optional)
  1. Meanwhile, in a large pot of boiling water, add 2 Tbsp Diamond Crystal kosher salt and cook 1½ cups uncooked elbow macaroni according to the package instructions, but cook 1 minute less than instructed as it’ll cook further in the frying pan. Drain well and set aside.
  2. If you’re using a broiler, preheat the broiler for 5 minutes. If you don’t have a broil setting in your oven, preheat the oven to 500ºF (260ºC). Adjust the rack so the food is about 4–6 inches from the heat source.
To Assemble
  1. Insert the wooden skewer to see if it goes through a piece of kabocha. If it does, add the white sauce and mix all together.
  2. Taste the sauce and season with Diamond Crystal kosher salt and freshly ground black pepper, if necessary.
  3. Add the cooked macaroni and mix well.
  4. Grease the inside of your 2 8- x 8-inch (20- x 20-cm) baking dishes with a stick of butter (or use 1 8- x 8-inch baking dish and 4 individual gratin dishes). You can also melt 1 Tbsp unsalted butter and use a brush to grease the dishes. Transfer the mixture to the buttered baking dish(es).
  5. Grate ½ cup Gruyere cheese on top and sprinkle ¼ cup panko (Japanese breadcrumbs).
  6. Place the baking dishes in the oven (broiler or 500ºF/250ºC) for 3 to 4 minutes until the top is nicely golden brown and bubbling around the edges. If the dishes are not browning evenly, rotate them around. Remove from the oven and let the gratin stand for 5 minutes. Garnish with chopped chives or parsley and serve.
To Store
  1. You can keep the leftovers in an airtight container and store in the refrigerator for up to 3 days and in the freezer for a month.

Nutrition Information

Calories 367kcal (18%) Carbohydrates 44g (15%) Protein 13g (26%) Fat 17g (26%) Saturated Fat 8g (40%) Polyunsaturated Fat 1g (6%) Monounsaturated Fat 5g (25%) Trans Fat 1g (50%) Cholesterol 37mg (12%) Sodium 215mg (9%) Potassium 709mg (15%) Fiber 4g (16%) Sugar 9g (18%) Vitamin A 1630IU (33%) Vitamin C 12mg (13%) Calcium 236mg (24%) Iron 2mg (11%)

Nutrition Facts

Serving: 8 individual

Amount Per Serving

Calories 367

% Daily Value*

Calories 367kcal 18%
Carbohydrates 44g 15%
Protein 13g 26%
Fat 17g 26%
Saturated Fat 8g 40%
Polyunsaturated Fat 1g 6%
Monounsaturated Fat 5g 25%
Trans Fat 1g 50%
Cholesterol 37mg 12%
Sodium 215mg 9%
Potassium 709mg 15%
Fiber 4g 16%
Sugar 9g 18%
Vitamin A 1630IU 33%
Vitamin C 12mg 13%
Calcium 236mg 24%
Iron 2mg 11%

* Percent Daily Values are based on a 2,000 calorie diet.