With a sharp knife, make a slit in the peppers from stem to tip, do not cut all the way through.
In a nonreactive pot, combine the vinegar, peppercorns, salt, sugar, cayenne, and bay leaves and bring to a boil. Add the peppers, onion, and garlic. Cook for 3 to 4 minutes until the vegetables wilt slightly. Remove from the heat.
Using tongs, pack the peppers snugly in 6 hot sterilized quart-size preserving jars. Evenly divide the onion, bay leaves, and garlic among the jars, tucking them in between the peppers. Fill each jar with the hot vinegar mixture to within 1/2 inch of the top. With a clean damp towel, wipe the rim and fit with a hot lid. Tightly screw on the metal ring. Process in a hot-water bath for 15 minutes.
Yield: 6 quarts