Wash the peppers, then cut off the tops and slice them into 1/2”-3/4” rings. Remove some of the seeds and discard.

Put peppers, garlic, peppercorns, red pepper flakes, sugar, and mustard seeds, in a quart-sized glass jar with an air-tight lid. Set aside.

Place water, vinegar, and salt in a medium saucepot and bring to a boil.

Pour the hot liquid into the jar with the peppers.

Stir gently and allow to cool before putting top on jar. Let jar sit at room temperature for about 24 hours.

Drain off any additional liquid at the top of the jar until the peppers are just barely covered.

Store refrigerated for 2-3 weeks before eating.