Chop the green tomatoes and onions.

Place the chopped tomatoes and onions in a large, deep stainless steel kettle or saucepan.

Sprinkle with pickling salt.

Let the mixture stand overnight.

In the morning, drain the mixture well, pressing out as much water as possible.

Return the drained mixture to the kettle.

Add granulated sugar, dry mustard, and pickling spices tied in a gauze bag.

Stir in white vinegar.

Cook the mixture slowly, stirring frequently, until the tomatoes are soft and clear (about 1 hour).

Bottle the chow chow in hot jars.

Process the filled jars in a boiling water canner for 10 minutes.