cook the relish
Finely chop the pickles and onion. Add sugar, cornstarch, pickle liquid, and cold water to a saucepan. Place over medium-high heat and simmer 6 - 8 minutes for the mixture to thicken.
Transfer the Pickle Relish to a jar and leave it to cool. Then transfer to a bowl and serve with hot dogs and burgers. Optionally, cover with a lid and store in the fridge.