6 lbs meyer lemons, washed
2.5 cups water
2 lbs (lbs, not cups!) sugar
~1 Tbsp thyme leaves, rinsed and pulled off the stems (I favor a sprinkling of thyme to play on my Mediterranean dreams of the Golden State, but the marmalade is just as lovely without)
Peel the zest from 2/3 of the lemons, and chop however finely you like (I like to remove tiny ribbons of peel directly from the fruit with a citrus zester, but if you want finished peels that are large enough to see in the finished product, use a regular peeler and then cut the removed peel into bits the size of your choosing). Be careful to remove only the peel, and none of the bitter white pith. Set the chopped zest into your marmalade pot and set aside.
Take the lemons and supreme them. If you haven't done this before, you can find a handy pictorial here, but this is the basic overview: Cut off the top and bottom of the fruit to form level surfaces, and then cut off all remaining pith and peel. Free the fruit from the membranes--with some citrus you'll have to cut the sections out, but with most meyer lemons you can just sort of tug them free with your fingers. Drop the naked, membrane-free fruit sections in your marmalade pot along with the zest. Place all membranes and seeds in a separate bowl. Discard the pith and extra peel. If there's any bits of fruit on the peel/pith you've trimmed, feel free to squeeze its juice into the marmalade pot. Bear in mind that the fruit segments will break down as they boil, so don't worry too much if you can't get them out in one piece.
Add the water to your marmalade pot, and bring to a boil over high heat. While the heat is coming up, lay out a large square of cheesecloth, and place all your membranes and pits therein. Tie it up with the kitchen twine, and add it to the pot. Bring to a boil, then reduce the heat to maintain a simmer for 10 minutes. Turn off the heat, and fish out the ball of seeds and membranes and set it on a plate to cool. When it's cool enough to handle, squeeze it to milk out the pectin. As you'll squeeze, a milky goo will ooze out. Exactly what you want! Let this goo plop back into the marmalade pot (don't worry if it sits strangely in blobs--it will melt once you reheat the marmalade). Squeeze the bag for a few minutes, until you've milked out a few tablespoons of pectiny goo. Add the sugar and thyme leaves, and bring the pot back to a boil.
Keep the pot at a good rolling boil until the marmalade sets. The amount of time this takes will vary, depending on the amount of pectin and water in the fruit. Count on at least half an hour, generally. It's done when a candy thermometer measures 220 degrees (the consistency will also have changed somewhat, and become more thick and syrupy). If you, like me, don't have a candy thermometer, you can do the cold plate test: Chill a plate in the freezer, and then drizzle a small amount of hot marmalade on it. Place it back in the freezer for a minute, then check it. Set marmalade doesn't need to be set like a jelly, but should be firm enough that it wrinkles slightly when you push it with your finger, and you can almost mound it, like slightly-thickened egg whites. Done! Pour into sterilized canning jars and process in a water bath for a shelf-stable product (and adored gift), or pour into any jars you like and store in the refrigerator.