Satsumaimo no ukishima / steamed bean paste cake with roasted sweet potato

This moist and gently sweet sponge cake is another great teatime companion. While it contains sweet bean paste, its egg and flour content lets it also complement Western meals when served as a dessert.  Below, I replaced some shiroan white bean paste with yakiimo roasted satsumaimo sweet potato, and threw in some apple bits cooked with mikan tangerine and cinnamon.

Whole recipe:
376 calories; 16.8 g protein; 5.9 g fat; 63.4 g carbohydrate; 52.6 g net carbs; 86 mg sodium; 196 mg cholesterol; 10.8 g fiber


<Ingredients>

(12 cm x 7.5 cm x 4.5 cm mold)

100 g shiroan sweet lima bean paste
50 g yakiimo roasted satsumaimo sweet potato paste (strained)
1 egg
1 tbsp rice flour
1 tsp granulated sugar
Apple filling (ingredients listed below)

For apple filling

1/4 apple (35 g in photo)
1/3-1/2 mikan tangerine (15 g in photo)
2 tsp erythritol
2 drops liquid stevia
1/16 tsp cinnamon

<Directions>
1.

Prepare apple filling.
Skin, core, and dice apple into 1-2 cm pieces.
Put apple, mikan pulp, erythritol, stevia and cinnamon in a microwaveable container.

Cover, and microwave for 1 minute to 1 and a half minutes until apple is cooked (becomes somewhat translucent). 

Remove cover, and microwave for another 1 minute or so until liquid is almost gone. 

Let cool.

2.

Line mold with parchment paper.

Bring water to boil for steamer.

3.

In prep bowl, place shiroan.
Separate egg white and egg yolk: place egg white in another bowl, and chill in freezer (or fridge).

Add egg yolk to shiroan through tea strainer. 

Mix shiroan and egg yolk well.

Add yakiimo paste to shiroan mixture, and mix well.

Add rice flour, and mix well.

4.

Add granulated sugar to egg white, and beat to make meringue.

Fold meringue into shiroan mixture, one-third at a time. 

Batter is ready.

5.

Pour 1/2 of batter in mold, and place apple filling.

Pour remaining batter.

Smooth surface with spatula. 

6.

Steam with cloth-wrapped cover positioned to let steam out at high heat for 20 minutes.

(After 20 minutes)

7.

Remove mold, unwrap parchment paper, and cool on rack.

<Notes>

• If steamer is not available, cake can be microwaved for 1 and a half minutes to 2 minutes (1,000 watts). Finished cake is a bit drier than one cooked in a steamer, but texture becomes somewhat moist by Day 2 (keep covered).
• If rice flour is not available, wheat flour works fine. When no flour is added, the cake crumbles easily, especially next to apple filling.
• Straining egg yolk is to remove membrane and opaque white parts to create a silky cake texture, but it is optional.
• Sweetness is on the light end and is largely determined by sweetness of yakiimo above; make sure to taste yakiimo first, and adjust the amount of sugar. More sugar (2-3 times) is recommended if you generally prefer sweeter taste or pairing with strong unsweetened tea. 
• Erythritol and stevia are granulated sugar substitutes. When granulated sugar is used to cook apple + mikan, nutrition figures for the whole recipe would be:  407 calories; 16.8 g protein; 5.8 g fat; 71.4 g carbohydrate; 60.6 g net carbs; 86 mg sodium; 196 mg cholesterol; 10.8 g fiber.
• Ukishima [lit. floating island] is the general name of bean paste sponge cake, and implies that the batter swells due to meringue while steaming. Ukishima is typically made with sweet bean paste (lima or azuki beans), egg, sugar and rice/wheat flour, and comes in various colors and patterns, often in combination with whole beans, nuts, fruit or yokan (bean paste jelly).

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