You'll need a little bit of prep time for this, say a couple hours, just enough to give the syrup time to cool down before adding it to your ice and bourbon. Or you can prep it the night before, and take a batch with you to your Derby Day celebration. You'll need to procure some Sweet Mint Organic Botanical Blend from Rishi Tea, plus some dried peppermint. Infuse two tablespoons of the Rishi blend plus 1 tablespoon of peppermint in 5 ounces of boiling water for about 5-10 minutes; the leaves will soak up about an ounce of water, so if you drop below 4 oz after removing the leaves, just add enough hot water to bring it back up to four. Add 1/2 cup of cane sugar to the still hot liquid, and stir until dissolved, ending up with about 6 ounces by volume. Bottle and cool until time to build your julep. If you can't locate the Rishi tea and don't feel like ordering it, but your favorite grocery carries Yogi brand tea, you can get by with their "Egyptian Licorice Mint" variety...2 teabags of that plus 1 tablespoon of dried peppermint should do it. Infuse as above.
Now, to build your drink, fill your Collins glass with cracked ice, add an ounce of your mint syrup, three ounces of bourbon (or rye if you live above the Mason-Dixon line, or if you just prefer rye), swizzle gently, top again with cracked ice, pour an additional 1/2 oz of your mint syrup on top, and let it sit for about five minutes before sipping. In case you're wondering just how much ice you'll need, the answer is "a lot," as I cracked an entire tray of ice for one Collins glass. On the plus side, the glass frosted itself after I swizzled it, which is always pretty damn cool! If you want to be really contrary, you can garnish with a mint sprig, but that'd be silly, after going through all that work to avoid using real mint leaves in the drink. Best to leave it ungarnished.
I must admit, prior to sampling this drink, I was worried that it would not have as much of a mint flavor as one might hope. Happily, it does. Plus, the addition of the other herbs in the infusion make for something a little more complex than your typical mint-sugar-water-bourbon Julep. If you really wanted to commit sacrilege and play up the licorice notes in your syrup, you could add a scant 1/8 oz of absinthe or Pernod or an anisette of some sort (or even Green Chartreuse). It would be a scandal if the word got out, but it would certainly bring a dollop of new life to that staid old grey mare of Derby tradition.