7 medium-sized dried chipotle chilies

⅓ cup chopped white or yellow onion

5 tablespoons apple cider vinegar

2 cloves garlic, sliced

4 tablespoons low-sodium ketchup

¼ teaspoon salt

3 cups boiling water

• Remove the stems and seeds from the chilies, and slit the chilies lengthwise. Roast in a heavy skillet over medium-high heat, turning them occasionally; heat until puffed and just beginning to get brown, about 10 seconds each. (Do not burn the peppers or the resulting sauce will be bitter.)

• Combine all of the ingredients in a nonreactive pan and pour the boiling water over them. Cover and cook over very low heat for 1 to 1½ hours, until the chilies are very soft and the liquid has been reduced to 1 cup. Freeze leftovers, or they can be kept for several weeks in the refrigerator in an airtight container.