How to Make It
Cook Brussels sprouts in a large stockpot of boiling water until bright green, about 5 minutes. Drain and rinse under cold running water. Bring 3/4 cup water, vinegar, and salt to a simmer in stockpot over medium; simmer until salt dissolves. Combine peppercorns, mustard seeds, sliced garlic, crushed red pepper, and bay leaf in a sterilized pint jar. Place Brussels sprouts in jar; add hot vinegar mixture. (You may have some leftover liquid.) Cool to room temperature. Cover with lid, and chill 4 days or up to 2 weeks before serving. Store covered in refrigerator up to 1 month.