This recipe, with quadrupled ingredients, except for water (reduced to 4 cups). Whole spices in all cases, since filtering out ground ones is next to impossible to do in a timely fashion in my experience. I would have used a mortar and pestle to crush them, but I don't have one so I just used my cutting board in conjunction with a rock I happened to have lying around (a polished one; I wouldn't want to use something rough, where powder would be likely to rub off in significant quantities). I also threw in about a teaspoon of poppy seeds (I doubt they have had a meaningful effect, I just wanted to use them; maybe more next time), a couple dried and crushed bird's eye chili peppers, a teaspoon of crushed cumin seeds, and about 12 crushed allspice corns. With the tea, I also put in about two teaspoons of lavender buds I had leftover from an old mead experiment. Omit the milk, and wait until after you filter out the spices to add the sugar (I learned this the hard way, since I wound up with a really slow-to-strain syrup that I had to push through by squeezing). You can strain it by pouring it into a storage container through a funnel with a doubled piece of cheesecloth in it.
You should wind up with a thick, brown syrup that's about 8x concentrated - dilute it with hot milk when you want a cup. No idea how long it keeps - hopefully longer than the week or so this should last me. At this concentration, the sugar should be a preservative.
I used teabags (19 - recipe calls for 24 after quadrupling and I think it would've been a bit better if I actually had that much) since that is what I had, and my experiences with tearing them open to free the contents result in impossible-to-strain sludge. If I start ordering tea in bulk, which I really should, I'll probably prepare cheesecloth pouches of the stuff to save trouble down the line.
EDIT: Also I didn't have bay leaves.