Mixed-Citrus Marmalade

Makes: 6 cups. Step 1: Slice citrus thinly using a mandoline. Remove seeds from slices and set aside. Stack slices and cut stacks of slices into quarters. Step 2: Put your pressure cooker on a large food scale and reset the scale to zero. Add sliced fruit and any accumulated juice to the pressure cooker. Record the weight of the fruit. Add water, then close and lock the lid. Step 3: Turn the heat up to high. When the cooker reaches pressure, lower the heat to the minimum needed to maintain pressure. Cook for 10 minutes at high pressure. Step 4: Remove from the heat and allow the pot to sit for 30 minutes before carefully releasing any residual pressure. Step 5: Put all of the seeds in a tea ball or gauze packet. Step 6: Calculate how much sugar to add by doubling the weight of the fruit. Pour the sugar into the uncovered pressure cooker over medium heat. Add the seed packet and stir constantly until the contents begin to boil. Boil everything together for about 5 minutes. Step 7: Discard seeds and ladle marmalade into hot, sterilized glass containers or jars, leaving 1/2 inch of headspace. Seal the containers or jars. Cool and refrigerate for a week or freeze.