Roll 160 g smooth red bean paste (koshian) into 20g balls. Cover and store in the refrigerator between steps.
Wash 8 strawberries and dry them thoroughly. Cut off the stems and place them on a sheet of kitchen paper.
Take the anko from the fridge and press each ball in the palm of your hand to make a flat circle and place a strawberry in the center.
Pull the edges of the bean paste up around the strawberry, leaving the tip slightly exposed.
Cover and refrigerate until later.
Mix 100 g glutinous rice flour and 60 g white caster sugar together in a microwavable bowl.
Pour 150 ml water into the bowl and mix until smooth.
Cover with plastic wrap and microwave for 1 minute 30 seconds at 600W.
Carefully peel back the plastic wrap. Use a spatula to scrape down the sides of the bowl and mix the cooked lumps into the rest of the mixture. Cover again and microwave for 2 minutes at 600W.
Being careful of the steam, peel back the plastic wrap and mix vigorously with the spatula until the mochi looks translucent. If there are still white bits, microwave in 20 second intervals. Let it cool until it's warm to the touch.
Coat a tray or chopping board with cornstarch and use the spatula to scrape the gyuhi (mochi dough) out of the bowl and onto the starch.
Sprinkle starch over the top of the mochi and roll it to 1cm thick. You can use your hands to stretch it or a rolling pin to roll it, just make sure to dust your chosen tools generously with starch. Cut the dough into equal pieces.
Coat your hand with starch and place one piece of mochi in the center of your palm. Place an anko coated strawberry in the middle with the point facing down
Pull the corners of the mochi over the base of the strawberry until they meet in the middle. Pinch them together until sealed. (Keep extra starch nearby in case it sticks to your fingers.)
Roll the finished mochi in your hand to neaten the shape and place it in a cupcake case, or on a sheet of greaseproof paper/container sprinkled with starch. Repeat until all the ingredients are used.
Wash your hands from time to time if they get sticky, then dry thoroughly before dusting with more potato starch.
Keep at room temperature and enjoy the same day!
Notes
Best stored at room temperature in an airtight container and consumed the same day.
If you have leftovers and you don't want to throw out your hard work, seal the mochi in a container and store in the warmest part of your fridge to eat the next day (24 hours max).
Make sure to have a bowl of cornstarch or potato starch nearby just in case the mochi gets stuck to your hands or tools. Wash hands from time to time if they get too sticky.
Try to use small/medium strawberries if you are making 8, larger strawberries will probably make only 4-6. (Consider this when cutting the "gyuhi" sweet mochi dough.)
If your dough cools too much, it might become prone to tearing. Heat in the microwave for 5-10 seconds to warm it slightly.