Koppa Mochi (Dried Sweet Potato Rice Cake)

Name: Koppa Mochi (Dried Sweet Potato Rice Cake)
Prep time: 30 min
Cook time: 50 min
Yield: 25 servings
Cuisine: Japanese
Ingredients: glutinous rice 2250 g; dried sweet potato koppa 3000 g; brown sugar 1000 g; white sugar 1000 g; salt 1 tbsp; water for soaking 4000 ml

Quick answer

Active time: 80 min
Waiting: See the steps
Level: Hard
Servings: 25 servings
Ingredients: 6

About this dish

Koppa, dried sweet potato, is rinsed, covered, and left for 6 hours so moisture spreads evenly through each piece, which is what lets it pound together with steamed glutinous rice into one smooth mass.

Equal weights of brown and white sugar sweeten the dough, which is pressed into a thick slab and cut once set.

Ingredients

servings

IngredientAmount

glutinous rice

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dried sweet potato koppa

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Instructions

5 steps

1

Wash glutinous rice three times until nearly clear, soak in 4L water under refrigeration for 8 hours, and drain for 30 minutes so its surface is no longer wet.
2

Rinse 3kg koppa quickly, place in a covered sieve, and rest at room temperature for 6 hours to equalize moisture.

If pieces remain brittle, mist with up to 100ml cold water in small additions.
3

Line two tiers of a fully steaming steamer with damp cloths and spread rice and koppa separately.

Steam rice for 35 minutes and koppa for 25 minutes, checking that each crushes easily between fingers.
4

Mash hot koppa in a mochi machine or mortar for 4 minutes, then add steamed rice.

Pound for 10 to 12 minutes until no large potato pieces or separate rice grains remain.
5

Add brown sugar, white sugar, and salt in three additions, pounding 2 minutes after each until absorbed.

Press into a damp mold 4cm thick, firm at room temperature for 4 hours, and cut into 25 pieces.