From America's Test Kitchen. This looked really interesting. The chipotle powder would probably be hard to find but Penzey's carries it online.
Ingredients
6 heads garlic (10 ounces), separated (about 100 cloves)
1-1/4 cups cider vinegar
1/4 cups sugar
1 tablespoon canning and pickling salt
1 teaspoon dried chipotle chile powder
1 teaspoon red pepper flakes
Instructions
1. Fill medium bowl with ice water. Bring 2 quarts water to boil in medium saucepan over high heat. Add garlic and cook for 1 minute. Transfer garlic to ice water and let cool for 2 minutes; drain well, discard ice, and peel garlic.
2. Bring vinegar, sugar, salt, chile powder, and pepper flakes to boil in now-empty saucepan over medium-high heat. Add peeled garlic, cook for 2 minutes, then immediately remove from heat.
3. Meanwhile, place two 1-cup jars in bowl and place under hot running water until heated through, 1 to 2 minutes; shake dry.
4. Using slotted spoon, pack garlic into hot jars. Using funnel and ladle, pour hot brine over garlic to cover. Let jars cool to room temperature, cover with lids, and refrigerate for at least 1 week before serving. (Pickled garlic can be refrigerated for at least 3 months; flavor will continue to mature over time.)