Peel onions and toss into a mixture of water and salt. Let stand overnight. Next day, rinse onions in several changes of cold water; drain and cut a slash halfway down from top of each onion. Pack into 5 sterilized pint jars, and over the tops sprinkle chopped green peppers, dried mint.

Mix remaining ingredients in a saucepan and cook to the boiling point; then reduce heat and cook very slowly for 30 minutes. Pour over the onions. Seal and store a minimum of 8 days before using. Give the jars a good shake every day during the mellowing period.