I buy my chai spices from World Merchants Spice www.worldspice.com
along with all of my herbs and spices. They wrote a great article on the history of chai and how to achieve the perfect fresh cup here http://www.worldspice.com/writings_pages/chai__brew.htm
They sell their own blends of chai spices, which is really just fresh, whole spices blended together, and they scoop out however much you order. I usually buy a couple of cups at a time, lol. However, they included the recipe for my favorite of their blends, the Roasted Chai, in their new book on herbs and spices. I recently tried it on my own and it was perfect. I've used the blend to make my own green tea chai, though you must drink it right away because green tea gets bitter if you let it sit too long. (though it does taste better with a good black tea) I use the whole spices, loose leaf green tea that I buy from adagio, splenda, and either whole milk or half and half, which ever I have on hand just for that purpose. I've tried it with skim milk, but it was horrible, in my opinion. World Spice even points out that the fat in the cream works as a flavor catalyst in the finished product. Lastly, this isn't a place to skimp on the milk. There's interesting flavor chemistry that happens between the butterfat of the (non-skim) milk and the tea leaf. The degree of creaminess in the cup is more than the sum of the milk parts added. I keep a small bottle of full-on, whole milk in the fridge just for making chai and the real cream comes out when I want to be particularly decadent. I save the skim for my cereal in the morning.
This recipe for the Roast Chai blend comes from fabulous book The Complete Encyclopedia of Herbs and Spices, by Tony Hill
(one of the owners of World Merchants Spice)
1 Tbsp coriander seeds
1 Tbsp fennel seeds
1 Tbsp cassia-cinnamon chips
1 1/2 tsp. whole cloves
1 1/2 tsp. cumin seeds
1 1/2 tsp. black peppercorns
Combine all the ingredients in a dry skillet and toast just until smoke appears; let cool. To use, crush in a mortar or pulse grind in a coffeee mill until the coriander seeds open.
To prepare: For 16 oz chai, add 1 heaping teaspoon of the just crushed spice blend to a small teapot. Glass French press style pots work well for this method, as long as you leave the press up to give the spices and tea leaves room to expand. Add 3/4 cup of just boiling filtered water, and wait 5 minutes while dreaming of India. Add 1 heaping teaspoon of black leaf tea, such as Asam, Nilgriri, or Yunnana, and top off with another 3/4 cup boiling water. Wait a time that's right for the tea you chose, say 3 minutes. This is a good time to dream of railway stations and the markets of Delhi. Strain the whole pot into 1/2 cup of warmed milk and sweeten to taste with sugar or honey. Enjoy the chai and remind yourself why you'll never, ever go back to those nasty premade concentrates.
I use splenda instead of sugar, but I did learn that skimping on the milk was a mistake. Sometimes I make it with green tea. As I mentioned, though, you have to be quick with green tea because it can become bitter. I tried to make some green tea chai to chill and it was horrible because it couldn't sit.