With the ear of corn on a cutting board, hold each cob upright in a bowl and cut off the kernels.  Then scrape the cob with the knife to extract the “milk solids.”

 

Transfer the kernels and milk to a food processor and puree for 2 minutes, scoping down the sides.  

Transfer the kernels and milk solids to a saucepan, add the salt, cornstarch, sugar, and water.  Bring to a simmer and stir until it is crisp-tender, four to five minutes.