Mochi Mousse — whipped cream with a soft mochi bounce

i. Origin & history

Mochi mousse has no long history or single inventor. It belongs to a broad and very recent trend in Japanese and wider East Asian cafés for 'mochi-textured' desserts — mochi-mochi being the Japanese word for that soft, bouncy, slightly sticky texture. Bakeries in Japan, Taiwan and Korea sell mochi-mochi breads, mochi doughnuts, mochi waffles and mochi cream puffs, and patisseries make mousse cakes with a layer of mochi or shiratama dumplings. Mochi mousse is one of the simpler expressions of the idea.

The approach rests on something traditional. Gyūhi — a soft, refined mochi made by cooking glutinous-rice flour with sugar and water rather than pounding steamed rice — has been made by Japanese confectioners for centuries, and is used to wrap delicate sweets because it stays soft longer than pounded mochi. Cooking a small amount of gyūhi and folding it into cream gives the mousse its faint stretch and chew.

Its flavourings come straight from the wagashi repertoire. Kinako and kuromitsu (dark sugar syrup) are the classic toppings for kuzumochi and warabimochi; red-bean paste is the filling of daifuku; matcha and hojicha are the flavours of almost every Japanese café. Mochi mousse borrows all of them and pairs them with the airy dairy textures of French pâtisserie, the same way Japanese bakeries have done since anpan.

Because the dish is new and loosely defined, recipes vary widely. Some are essentially a set cream with a mochi layer; others, like this one, mix the mochi paste into the mousse itself so that every spoonful has a slight elastic pull.

ii. How a rice-flour paste changes a mousse

A classic mousse is whipped cream or egg foam stabilised with gelatine or chocolate. It is light and melts quickly in the mouth. Adding cooked glutinous-rice paste changes the texture: the amylopectin starch in glutinous rice forms an elastic gel when cooked, and when that gel is dispersed through the cream it gives the mousse a soft spring and slight cling, rather than a clean melt.

The paste must be fully cooked. Raw rice flour tastes chalky and does nothing for the texture; cooked until glossy and translucent, it is smooth and stretchy. It is cooked with water and sugar over low heat, stirred constantly, just like gyūhi. The sugar keeps it soft and slows the hardening (retrogradation) that happens to all cooked starch in the fridge.

The tricky step is combining a sticky paste with a delicate foam. The paste is loosened first with a little milk while it is still warm, then cooled to body temperature. Too hot, and it melts the cream; too cold, and it sets into lumps that will not fold in. Mixing a spoonful of the whipped cream into the paste first lightens it, so the rest folds in smoothly.

Gelatine provides the set. Without it, the mousse slowly weeps and slumps; with a modest amount, it holds its shape in the glass for a day or two while still feeling soft. Agar can replace it, but gives a firmer, more brittle set.

iii. Ingredients

Makes 6 servings · scroll the side panel to adjust

• 4 g leaf gelatine (about 2 sheets) or 4 g powdered gelatine
• 50 g shiratamako or mochiko (glutinous-rice flour)
• 60 g caster sugar
• 100 ml water
• 100 ml whole milk
• ⅛ tsp salt
• 250 ml double or whipping cream, chilled
• 2 tbsp kinako, plus extra for dusting
• 120 g sweet red-bean paste, to serve
• 3 tbsp kuromitsu or dark muscovado syrup, to serve

Shiratamako gives the smoothest, most elastic paste; mochiko or Thai glutinous rice flour also work. Ordinary rice flour will not. Kinako gives a toasted, nutty flavour reminiscent of peanut; omit it for a plain vanilla mousse or replace it with 1 tbsp matcha or hojicha powder. Kuromitsu is a Japanese syrup of kokuto (Okinawan black sugar); a syrup of dark muscovado melted with an equal weight of water is a fair substitute. For a vegetarian set, replace the gelatine with 1 g agar powder boiled with the milk.

iv. Method

1. Soak leaf gelatine in cold water for 5 minutes, or sprinkle powdered gelatine over 2 tbsp cold water and leave to swell.
2. Whisk the glutinous-rice flour, sugar and water in a small non-stick saucepan until smooth. Cook over low heat, stirring constantly with a spatula, for 3–5 minutes, until the mixture turns into a thick, glossy, translucent paste.
3. Take off the heat and gradually beat in the milk, a little at a time, until smooth and loose. Add the salt and the squeezed gelatine leaves or swollen powder, and stir until dissolved.
4. Sift in the kinako and whisk until smooth. Cool, stirring occasionally, until just lukewarm, about 30 °C — it should feel neither warm nor cold on your lip.
5. Whip the cream to soft peaks. Stir 2 large spoonfuls into the rice mixture to loosen it, then fold in the rest of the cream in two additions until smooth and evenly coloured.
6. Spoon a teaspoon of red-bean paste into the base of 6 small glasses, then divide the mousse between them. Tap to level, cover and chill for at least 4 hours, until set.
7. To serve, top each with a little more red-bean paste, a drizzle of kuromitsu and a dusting of kinako.

v. Tips & common mistakes

• Cook the paste until fully translucent. Any white, opaque streaks mean raw flour, which tastes chalky.
• Loosen with milk while warm. Thick mochi paste does not fold into cream; beating in milk while it is warm keeps it smooth.
• Cool it to lukewarm before folding. Too hot melts the cream; too cold leaves gelatinous lumps.
• Whip the cream to soft peaks only. Firm peaks are hard to fold into a heavy base and turn grainy.
• Sift the kinako. It clumps easily and leaves dry pockets in the mousse.
• Serve within two days. The starch slowly firms in the fridge and the mousse loses its softness.

vi. Variations

Matcha mochi mousse replaces the kinako with 1 tbsp sifted matcha and pairs well with red-bean paste. Hojicha mochi mousse uses roasted green tea for a toasty, caramel note. A black sesame version swaps the kinako for 2 tbsp black sesame paste — see black sesame ice cream for the same flavour frozen. Add small chewy shiratama dumplings on top for a stronger mochi texture, or layer the mousse with fruit and jelly in a parfait glass like anmitsu.

For other mousses, see the white chocolate mousse and hazelnut mousse; for chewy Japanese textures in their traditional forms, try kuzumochi or mochi itself.

vii. Serving & storage

Serve mochi mousse chilled, in small glasses or cups, with a spoon and green tea. It works as a dinner-party dessert because it is made in advance and finished at the table with toppings.

Covered, it keeps for up to 2 days in the fridge. Add the kinako and syrup only just before serving; kinako absorbs moisture and turns pasty if left on the surface. The mousse does not freeze well — the starch turns grainy when thawed.

ix. More from Japanese

• Kuzumochi — kudzu starch jelly with kinako
• Daifuku — mochi with bean paste
• Anmitsu — agar jelly and fruit parfait
• Mochi Cheesecake — chewy baked cheesecake
• Espresso Panna Cotta — set coffee cream
• White Chocolate Mousse — airy white chocolate cream