Preparing the plums

1. First, wash the ume thoroughly with warm water. 
   
2. Wash your hands thoroughly and take a few clean tea towels. Use one tea towel to dry the plums and one or two to lay them out.
   
3. While drying the plums, remove the stems with a cocktail stick. (If they're left in, the syrup can become bitter.) 
   
4. Once all of your plums are dry and destemmed, place them in a ziplock bag or sealable container and store them in the freezer for at least 24 hours. 
   

Making the Syrup

1. First, sterilize your jar by filling it with boiling water and letting it sit for a few minutes.
   
2. After a few minutes, pour the liquid out. (Pick up the jar using oven gloves as the glass will be very hot.)
3. Place the jar on a clean drying rack and allow to air dry. (If you're impatient, wipe with a paper towel blotted with some alcohol.)

   

4. Place a layer of frozen ume at the bottom of the jar, then top them with a layer of the rock sugar.
   
5. Keep adding layers of plums and sugar until the glass is full. 
   
6. Seal the lid tightly and then store in a cool dark place. (Cupboards or basements are perfect.)
7. Make sure to tilt the jar everyday to move the sugar and plums around. 
8. Your ume syrup will be ready in 7-10 days.
   
9. Enjoy in a drink (mix 1 part syrup with 4 parts water/soda) or pour over shaved ice, yogurt, etc.
10. After 3 weeks, remove the ume.
    TIP: If your syrup still has lumps of sugar, transfer it to a pan and heat it on the stove on a low heat until it's all dissolved. You can then transfer it to a smaller sterilized jar.
11. Keep in a cool dark place for up to 3 months, or up to 1 year in the fridge!