Updated recipe from best cassina brew I've made yet

Yesterday when preparing a pot of the Black Drink for students in my Southeastern Indians class, I used a ziploc bag full of previously-parched, whole cassina leaves (Ilex vomitoria), which I had put away several weeks back after picking out the black (burned) leaves.  Dumping the entire quantity (perhaps 1/2 cup or a little more) into a pot with 4 cups of water, I let the leaves boil on just-below-high heat for about 45 minutes, stirring occasionally to free the leaves from clumping up on the sides.

When I poured the product through a strainer into a bowl, the color was very dark brown, like strong coffee.  Poured into a large thermos bottle, the tea kept piping hot for at least 10 hours or so, and was definitely the best I've ever brewed, with none of the bitter aftertaste I've come to expect from the Black Drink.  I'm not sure whether it was sorting out all the most burned leaves after parching, or letting it sit for many weeks in a ziploc bag before boiling it, but the concoction was just about perfect in my opinion (and a few students came back for more).  Perhaps some of the oils had time to evaporate or dry up, just enough to ameliorate the strong edge in flavor.

Here's the current recipe in short form:

How to Brew Cassina Tea, a.k.a. the Black Drink
1. Gather several small outer branches from live Yaupon Holly shrubs (Ilex vomitoria), setting them on a tray to dry for about a week.
2. Gather all dried leaves, separating leaves still attached to the stems and removing all stem bits.
3. Rinse leaves in a strainer, and set on a towel or paper towel to dry.
4. Parch leaves in a cast iron skillet over medium heat (the oven fan is very useful here), stirring constantly and keeping the leaves in motion to keep the lower leaves from browning too much.  The pan will smoke during this process
5. When the leaves have turned more brown than green (and before the leaves char), remove from skillet into a tray to cool.
6. Separate the blackest leaves and discard; bag the rest of the leaves in ziploc bags for later use (a month or more seems to produce the best results).
7. To brew a pot of cassina, take 1/2 cup (or slightly more) of the previously-parched leaves, place them in a saucepan with 4 cups of cold water, and heat on medium-high heat until boiling.  Let boil for 45 minutes or more, until liquid turns dark brown, stirring to keep the leaves from clumping or sticking to the sides.  Add water as needed to maintain the liquid volume at 4 cups.
8. Remove pan from heat and pour hot tea through a strainer into a metal bowl.
9. Add 4 Tbsp. sugar (more or less to taste) for the 4 cups of tea, stir, and serve immediately or place in thermos to serve later or transport.