Basically anything ending in "imo" in Japanese means potato, and satsuma-imo are sweet potatoes. You will find roasted sweet potato carts all over Tokyo during certain times of the year or at festivals (Spring and probably Fall particularly). The cart-mongers have a clay oven in the back on wheels and roll around town with the smell of sweet potatoes baking wafting from their cart (this is much more effective than the ice cream man's tune).
Back state-side, you can approximate this by roasting sweet potatoes in the oven under the broiler. I figured I'd give it a try and put the roasted potato into a sort of cake, and was inspired by this recipe. I'm still working out the specifics... so no promises!
Roast 1 sweet potato in the oven either at 400 F for 40minutes to 1 hour, or under the broiler until the top gets browned and a fork moves easily into the flesh of the sweet potato.
Combine in a bowl and mash with a fork:
200 g mashed, roasted sweet potato (this is about one small sweet potato)
50 g (or about 1/4 C) mochi flour 2.5 TB softened butter
Now mix in:
2 eggs (beaten)
3/4 C sweetened condensed milk 1/3 C rice milk (could sub in coconut milk, cream or buttermilk)
1 tea vanilla
Pour into a small cake/tart pan (about 5" x 18" x 1" deep).
Bake at 350 F for 20-30 minutes or until cake is set and a toothpick inserted into the middle comes out clean.
Couple ideas I might try next time:
- reduce the amount of sweetened condensed milk, and sub in more rice milk and some molasses
- add nutmeg, cinnamon or cloves
- add turmeric for color