Recipe Instructions:
2 pounds (1 kg) quince (or apples), on the underripe side
1 1/2 cups (300 grams) sugar
1/2 lemon, sliced (optional)
mustard essence, as needed (10-20 drops per kilogram of cooked fruit)
Directions
Day one: Peel and finely chop the fruit. Place in a non-reactive bowl with the sugar and lemon slices (if using) and toss until well-combined. Leave to sit in a cool place to macerate for 24 hours.
Day two: Strain the liquid created by the fruit into a small saucepan. Return the fruit to the bowl. Bring the liquid to a rapid boil, cook for 5 minutes. Remove from the heat and pour the liquid over the fruit. Let cool, then cover and let sit in a cool place for another 24 hours.
Day three: Strain off the liquid again, into a saucepan. Return the fruit to the bowl. Bring the liquid, which should be more syrupy now, to the boil and cook 5 minutes. Pour it back over the fruit. Let cool, then cover and let sit in a cool place for 24 hours.
Day four: Place the fruit and its syrup in a saucepan and bring to the boil. Turn the heat down to a simmer and let cook, turning the fruit with a wooden spoon to cook it evenly, for about 10 minutes (if there is not enough liquid left to cook the fruit through, add a splash of water to help it along). The fruit should still have some bite to it, it should keep its shape, but be evenly cooked. It should all be held together with a light syrup.
Let it cool completely, then, weigh the fruit (you do need scales for this! In my experience with this recipe, it produces about 750 grams of cooked fruit, so 3/4 of a kilogram). In a well-ventilated area, open the bottle of mustard essence (do not put your face close to it or try to sniff it directly and do not try to taste it or get it on your skin!) and carefully add 10-20 drops of mustard essence per kilogram of fruit or to taste—10 drops will produce a mildy spiced mostarda, 20 is not for the faint hearted! I would recommend 10-12 drops per kilogram (so 8-9 drops for 3/4 of a kilogram of cooked fruit). Bottle in sterilised jars and, if not planning on eating within the month, process the cans to seal. This is best consumed within six months as the mustard essence begins to weaken significantly after this time, even if unopened. As the essence diminishes with heat, it is best to keep the mostarda somewhere cool.
