Japanese-Style Sweet Potato Gratin- Japanese Home Cooking and Sweets Class in Tokyo

This Japanese-style cream gratin combines the natural sweetness of sweet potato and the mellow richness of soy milk with the gentle, sweet-salty flavor of white miso. Adding chicken or mushrooms makes it a satisfying main dish for an autumn meal.

Ingredients (Serves 1–2)

• Sweet potato: 200 g

• Onion: 1/4

• Shimeji mushrooms: 1/2 pack (optional)

• Butter: 10 g

• Cake flour: 1 1/2 tablespoons

• Unsweetened soy milk: 200 ml

• White miso: 1 tablespoon

• Salt: a pinch

• Black pepper: a pinch

• Meltable cheese: 40–50 g

• Optional: black sesame seeds, nuts, parsley

Dissolving the white miso in a small amount of soy milk beforehand helps prevent lumps and allows it to blend more easily into the sauce.

Instructions

1. Prepare the sweet potato

Wash the sweet potato well and cut it into 1-cm cubes, or into thin half-moon slices about 5 mm thick. Place in a heatproof container, cover loosely with plastic wrap, and microwave at 600 W for about 3 minutes, until a skewer slides in easily.

2. Sauté the vegetables

Melt the butter in a frying pan and add the onion. Sauté until softened.

3. Make the soy milk sauce

Reduce the heat to low and add the cake flour. Cook, stirring, until the raw flour taste disappears. Add the soy milk in 3–4 additions, stirring well after each addition, until the sauce thickens.

4. Season with white miso

Add the white miso dissolved in a small amount of soy milk, along with salt and black pepper. Avoid bringing the soy milk to a rolling boil, as it can separate. Cook over low heat for 2–3 minutes, until the sauce is smooth and creamy.

5. Assemble and bake

Add the sweet potato and mix gently. Transfer to a gratin dish, top with the cheese, and bake in a toaster oven for 5–7 minutes, or in an oven preheated to 230°C for about 10 minutes, until the surface is golden brown.

Tips for Success

• Cook the sweet potato first: If you simmer it in the sauce, it may lose its shape and become watery.

• Do not overheat the white miso: Its delicate flavor fades easily, so add it after the sauce is ready.

• Add the soy milk gradually: This prevents lumps and gives the sauce a smooth, silky texture.

• Adjust the sweetness as needed: If your sweet potato is very sweet, reduce or omit the honey and season mainly with the saltiness of the white miso for a more refined flavor.

Variations

• Shrimp or scallops: These pair beautifully with white miso and soy milk, making the gratin feel a little more elegant.

• Breadcrumbs or nuts: Sprinkle breadcrumbs or sliced almonds over the cheese for extra aroma and crunch.