Add toasted sesame seeds into a mortar and grind until halfway ground
Add tamari, mirin, and sugar and mix well
Add water and a tsp salt to a medium pot and boil
Wash spinach well to remove dirt from between the leaves
When water is boiling, arrange spinach so all stems are bunched together and insert only the stalks into the boiling water for 1-2 minutes
After 1 minute, dunk the rest of the spinach leaves under water and cook for another 1-2 minutes
Strain spinach and immediately add to ice water bath to cool down and stop the cooking process
Once cooled, squeeze out excess water and cut the spinach into 1.5-2 inch chunks
Add spinach to a bowl, add sesame dressing and mix well
Leave in fridge and remove about 30 minutes before serving to warm up to room temperature
