Rinse plums under warm water. Cut each plum in half, remove the pits, and chop into small pieces.

Wash at least one hot pepper (e.g., jalapeño) under warm water. Halve, remove the seeds, and chop into small pieces.

Chop ¾ cup of onion (white or red, based on preference) and finely chop two garlic cloves.

In a bowl, measure 2 cups brown sugar, 1 cup white sugar, 2 tablespoons mustard seed, 1 tablespoon salt, and 1 teaspoon dried ginger.

Measure 1 cup of cider vinegar.

Place the chopped plums, peppers, onion, garlic, the measured sugars, mustard seed, salt, dried ginger, and cider vinegar into a stainless steel saucepan. Stir gently to combine all ingredients evenly.

Set the burner to medium-high heat. Bring the mixture to a boil, stirring constantly to prevent scorching. Lower the heat and simmer for nearly 2 hours, stirring regularly until the sauce thickens and coats the back of a spoon.

While the sauce cooks down, wash and inspect eight half-pint jars for damage. Sterilize the jars in your water canner filled with hot water over medium heat. Warm the lids in a small saucepan over low heat to soften the adhesive.

Once the sauce has thickened, remove the jars from the canner using a jar lifter and place them on a clean, warm surface (avoid cold countertops). Using a canning funnel and ladle, fill each jar with the hot sauce, leaving ½ inch of headspace for expansion. Remove any air bubbles by running a knife around the jar edges.

Wipe the rims of each jar with a damp paper towel to remove any spills. Place the warmed lids on the jars and screw on the rings until they are finger-tight.

Place the filled jars back into the water canner, ensuring they are covered with at least 1 inch of boiling water. Process for 10 minutes (adjust the time for your elevation if necessary).

After processing, turn off the heat and let the jars sit in the canner for 5 minutes to stabilize. Remove the jars with a jar lifter and place them upright on a cutting board or towel to cool undisturbed for 24 hours.

After 24 hours, check each jar by pressing the center of the lid. If the lid does not pop back, it is sealed properly. Label each jar with the date and store them in a cool, dark place.