Roasted Japanese yams with chestnut curry sauce

Serves 8

Japanese curry powder is available at Kotobukiya market in Cambridge (617-354-6914); myoga and shiso usually are, but call ahead to make sure. If you can't get Japanese yams, use regular sweet potatoes.

POTATOES

3	large sweet potatoes, peeled (about 3 1/2 pounds)
	Salt and pepper, to taste
3	tablespoons grapeseed oil

1. Set the oven at 400 degrees. Slice the sweet potatoes crosswise into 3/4-inch rounds. You need to make 24 slices. Sprinkle with salt and pepper. Set aside for 1 minute.

2. Transfer the sweet potato slices to a shallow bowl. Sprinkle with oil and turn the slices to coat them. Set the potatoes on a nonstick sheet pan in a single layer. Roast them for 20 minutes or until they are just tender when pierced with a skewer.

3. Remove the potatoes from the baking sheet with a wide metal spatula and transfer to a serving platter.

SAUCE

5	tablespoons unsalted butter
1	onion, finely chopped
1	clove garlic, finely chopped
1	1-inch piece fresh ginger, peeled and chopped
1	small carrot, finely chopped
2 1/2	tablespoons Japanese curry powder
2 1/2	cups chicken stock
1/2	small russet potato, cut into 1/4-inch dice
1/2	small ripe mango, cut into 1/2-inch dice
6	canned chestnuts
3	tablespoons chestnut liquid (from the can)
	Salt, to taste
1 1/2	tablespoons sugar
2	bulbs fresh myoga, very thinly sliced (for garnish)
4	leaves fresh shiso, very thinly sliced (for garnish)

1. In a saucepan, melt the butter. Add the onion, garlic, ginger, and carrot. Cook on medium-low heat, stirring often, for 3 to 4 minutes or until slightly softened. Do not let the mixture brown.

2. Add the curry powder and continue cooking on low heat, stirring constantly, for 1 minute. Stir in the stock. Add the potato, mango, chestnuts, chestnut liquid, salt, and sugar. Bring to a boil, lower the heat, and simmer for 7 to 8 minutes or until the potatoes and carrots soften. Remove the pan from the heat. Set aside for 30 minutes.

3. In a blender, puree the curry mixture until smooth. Transfer to a clean saucepan and reheat before serving. Spoon the curry sauce over the sweet potatoes. Garnish with myoga and shiso. - Adapted from Tim Cushman of o ya