It turns out there are a lot of nifty things one can do with an etrog once Sukkot is done. Some folks poke them full of little holes, embed whole cloves, and use the ensuing pomander ball as their besamim (sweet-smelling spices) in havdalah thereafter. One reader commented here with a recipe for making limoncello that involves fifteen etrogim, a bunch of sugar, and some good vodka...and an eighty-day interim between preparation and consumption! But once my eye fell upon this etrog-ginger marmalade recipe, my path was set: preserves it would be.
I didn't realize until I was a few steps in to the recipe that the instructions are a little bit skimpy. The ingredient list includes four cups of sugar, for instance, but the instructions never mention adding it. (Whoops.) So while the slices of lemon and etrog were simmering, I did some quick googling for other etrog marmalade recipes (this one includes oranges and a grapefruit, mmm) to figure out when the sugar ought to be added. I'm glad I caught that; I would have wound up with some painfully sour preserves otherwise!
The recipe also doesn't tell you how much it yields. I sterilized two pint jars and two jelly jars, which turned out to be just right. All four of my jars sealed beautifully, with that satisfying popping sound that makes a home-canner's heart soar. And the stuff is beautiful, golden-yellow and spiked throughout with little suspended slices of fruit. Only trouble is, it looks more like syrup than like marmalade. We do a lot of pickling, but I've only made jam once or twice before (and never with sugar and liquid pectin.) Clearly I haven't mastered that part yet, since the marmalade didn't "set". Looks like I should have tested a spoonful and added more pectin as necessary until it was sufficiently thick.
Oh well; you win some, you lose some. I've got four jars of lemon-etrog-ginger fruit sauce, instead. It tastes lovely, and I imagine the flavors will intensify and marry as it sits on the shelf. It'll be excellent on vanilla ice cream, or waffles, or bread pudding, or potato latkes at Chanukah. And I like to imagine how golden-autumnal these "fruits of goodly trees" will taste at Tu BiShvat, when the world around us is covered with snow and the trees are still sound asleep, dreaming of the time when the earth will thaw and the sap will begin to rise.