Sake Kasu Castella Cake – Recipe

Remember the time I won a Japanese sake cooking competition and flew to Kyoto to learn about brewing sake? Two years on I still have some sake kasu – the fermented rice solids left over from the sake filtration process – in deep freeze from when I bought it over there. And to my surprise, it's still perfectly fine. So I decided to do another recipe with it, this time in the form of a castella cake – Japan's favourite sponge cake.

The sake kasu lends a slightly sweet aroma of sake with a hint of umami. If you can't get sake kasu to make the amazake mixture, you can use ready made amazake instead.

Ready? Let's go.


6 large eggs
220g caster sugar
220g plain flour
150ml amazake, made from 100g sake kasu dissolved in 300ml water (or 150ml ready made amazake)


1. Preheat the oven to 170°C, and grease and line the bottom and sides of a deep 8" square cake tin with baking parchment (greasing the sides makes the parchment stick to the sides).

2. Whisk the eggs and sugar together in a large bowl sitting over a pan of simmering water until very thick and fluffy, almost like a meringue.

3. Take the bowl off the heat and fold in the flour and amazake. Pour into the tin, swirl the batter with a knife to get rid of large air bubbles, and place the tin in a roasting tray half-filled with hot water to create another water bath.

4. Bake for 15 minutes, then turn the heat down to 150°C and bake for a further 30 minutes, or until the cake springs back when you poke it lightly.

5. Flip upside down onto a cooling rack, keeping the tin on to keep the cake moist, and leave until completely cooled.

6. Invert onto a serving plate, peel off the baking parchment, trim the edges and cut into even slices.

Enjoy, and have fun.


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