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1
Place the lemon eighths in a nonreactive saucepan where they will fit snugly in a single layer.
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2
Add enough cold water for the fruit to bob freely.
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3
Cover tightly and let rest overnight at room temperature.
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4
Prepare the cooked lemon juice: Bring the lemon eighths to a boil over high heat, then lower the heat to medium.
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5
Cook the fruit at a lively simmer, covered, for 2 to 3 hours, or until lemons are very soft and the liquid has become slightly syrupy.
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6
As the lemons cook, press down on them gently with a spoon every 30 minutes or so, adding a little more water if needed.
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7
The water level should stay consistently high enough for the fruit to remain submerged and float freely as it cooks.
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8
When the lemons are finished cooking, strain their juice by pouring the hot fruit and liquid into a medium strainer or colander suspended over a heatproof storage container or nonreactive saucepan.
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9
Cover the entire setup well with plastic wrap and let drip overnight at room temperature.
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10
Meanwhile, prepare the kumquats: Place the kumquat quarters in a wide stainless steel kettle and add cold water to reach 1 inch above the tops.
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11
Cover tightly and let rest overnight at room temperature.
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12
Place a saucer with 5 metal teaspoons in a flat place in your freezer for testing the marmalade later.
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13
Bring the pan with the kumquats to a boil over high heat, then decrease the heat to medium and cook, uncovered, at a lively simmer until the fruit is tender, 15 to 30 minutes.
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14
Remove the plastic wrap from the lemon eighths and their juice and discard the lemons.
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15
Strain the juice well through a very fine-mesh sieve to remove any lingering solids.
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16
In a large bowl, combine the sugar, cooked lemon juice, kumquats and their liquid, and 1/4 cup of the fresh lemon juice.
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17
Stir well.
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18
Dip a small spoon into the syrupy liquid and taste the liquid.
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19
If you do not detect a bright, tart lemon flavor, cautiously add a bit more lemon juice, stirring and tasting as you go, until you can just taste the tartness and lemon flavor of the juice in the mixture.
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20
Once you have reached this point, the mixture is ready to cook.
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21
Transfer the mixture to an 11- or 12-quart copper preserving pan or wide nonreactive kettle.
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22
Bring the mixture to a boil over high heat.
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23
Cook at a rapid boil until the setting point is reached; this will take a minimum of 25 minutes but may take longer, depending on your individual stove and pan.
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24
Initially, the mixture will bubble gently for several minutes; then, as more moisture cooks out of it and the sugar concentration increases, it will begin foaming.
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25
Do not stir it at all during the initial bubbling; then, once it starts to foam, stir it gently every few minutes with a heatproof rubber spatula.
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26
As it gets close to being done, stir it frequently to prevent burning, loewring the heat a tiny bit if needed.
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27
The marmalade is ready for testing when its color darkens slightly and its bubbles become very small.
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28
To test the marmalade for doneness, remove it from heat and carefully transfer a small representative half-spoonful to one of your frozen spoons.
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29
It should look shiny, with tiny bubbles throughout.
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30
Place the spoon back in the freezer for 3 to 4 minutes, then remove and carefully feel the underside of the spoon.
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31
It should be neither warm nor cold; if still warm, return it to the freezer for a moment.
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32
Tilt the spoon vertically to see whether the marmalade runs; if it does not run, and if its top layer has thickened to a jelly consistency, it is done.
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33
If it runs, cook it for another few minutes, stirring, and test again as needed.
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34
Turn off the heat but do not stir.
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35
Using a stainless steel spoon, skim off any surface foam and discard.
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36
Pour the marmalade into sterilized jars.
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37
This recipe yields 2 1/2 quarts.
