Cook the short-grain rice according to package directions, then spread it out to cool.

In a large bowl, combine the malted barley powder with 10 cups of lukewarm water. Let it steep for 30 minutes, stirring occasionally.

Strain the malted barley mixture through a fine-mesh sieve or cheesecloth into a large pot, discarding the solids. This is your "barley water".

Add the cooled cooked rice to the barley water in the pot.

Heat the pot over low heat (or use a rice cooker on 'warm' setting or an Instant Pot on 'yogurt' setting for 3-4 hours) until about 5-7 grains of rice float to the surface when stirred. This indicates successful starch conversion. Do not boil.

Once rice grains float, carefully scoop out the floating rice grains and rinse them under cold water. Set aside for garnish if desired.

Bring the remaining liquid in the pot to a boil over medium-high heat, then reduce heat and simmer for 10-15 minutes, skimming off any foam.

Stir in the sugar until dissolved. Taste and adjust sweetness as needed.

Remove from heat and let it cool completely. Store in the refrigerator.

Serve chilled, optionally garnished with the reserved rice grains and a few pine nuts.