Making malt water (Choose one of the two methods below)
Simply put the malt barley in a cheesecloth bag (or nut milk bag), and place the bag in 12 cups (can be more if your bowl is large enough) of warm water in a large bowl for 20 to 30 minutes. Then, massage and squeeze the bag to extract milky grain contents until the liquid is milk color.
Alternatively, use a fine sieve. Place the malt barley in a large bowl, and stir in 12 cups (or more) of warm water, and let it sit for 20 to 30 minutes. Rub the malt between your palms and squeeze out milky liquid. Filter the liquid through a fine sieve (or lined with a cheesecloth). Then, squeeze the strained malt husks in the sieve with your hands to drain out the remaining liquid.
Let the malt water sit for 15 to 20 minutes for some sediments to settle at the bottom, longer if you want very clear liquid.
Place the bag (or the residual malt husks if you used a strainer) in another 12 cups of warm water in another bowl and repeat the process to make more malt water.
Cooking rice
Cook 1 cup of rice with a little less (about 10% less by volume) water than your normal amount. The cooked rice should be a bit drier than your normal cooked rice. You don't need to pre-soak the rice for this recipe. Fluff it up when cooked.
Steeping
Carefully pour the malt water into the rice cooker, leaving the sediments at the bottom. Stir to combine the malt water, breaking up the rice clumps. My rice cooker can easily hold 18 cups of water. Close the lid and press the “keep warm” setting.
After about 4 hours, open the lid and check to see if about 10 rice grains float at the top. It can be many more. If not, close it and leave it for another 30 min to 1 hour (or longer) as necessary. A grain of rice between your thumb and index finger, the grain should roll like a piece of yarn, not slippery starchy grain, when ready.
Boiling
Carefully transfer to a stockpot. You can run it through a strainer if you want to keep some rice separately for the optional step below.
Optional step if you want to have some floating rice grains when serving: Strain out some rice from the sikhye. Rinse the rice grains in cold water, changing the water a couple of times. This removes malt contents the grains picked up while being steeped and makes them lighter. Keep them in a container with enough fresh water to cover. Store in the fridge.
Bring the sikhye to a boil, removing the foam. Add the sugar and optional ginger slices to taste. For about 20 cups of sikhye, I use 3/4 cup, but this is much less than the amount that’s usually used for sikhye. Adjust to taste. Continue to boil for about 5 to 6 minutes.
Instant Pot Option
You basically do the same steps as noted above for the rice cooker. Start with cooking the rice in the Instant Pot using the "rice" function. Fluff it up, and gently add the malt water, leaving the sediments at the bottom. My 6 quart Instant Post can hold 18 cups of water. Stir well to break up the rice clumps. Close the lid, and press the "keep warm" button. Open and check in 4 hours. If there are about 10 rice grains floating, it's ready to be boiled. This is the minimum point, and it can be many more grains floating and more hours. You can simply boil it in the Instant Pot using the sauté function if that's all the sikhye you want to make.
Variations
Danhobak sikhye: Simply cook the whole kabocha in the microwave (about 10 minutes) until tender to touch, remove the skin, and puree the flesh in a blender or with an immersion blender with 2 cups of the malt water or sikhye.
Purple sweet potato sikhye: Simply add 3 tablespoons of the purple sweet potato powder (or to taste) while boiling the sikhye.
Storing
Sikhye keeps well in the fridge for 5 to 6 days or longer, depending on your fridge. To be safe, you can boil it again for a few minutes after 5 or 6 days or freeze it in freezer bags for longer storage.