You can try finding the powder at an Asian grocery store. The one I frequent has a section of powders that seem like they might be geared more toward a consumer than a restaurant. I just checked: it's a one pound bag. I was able to buy just the one bag, but it was a while ago, so I don't recall the price. According to the bag, the ingredients are Non-dairy creamer, (whatever flavor - I have strawberry and almond) powder, glucose, and coloring. Even though it says it has glucose, you're still supposed to add sugar according to the directions (and it definitely needs it).
As for creaminess, you might consider trying milk/soy milk/almond milk, etc. instead of water. When ever I've made it, it turned out much better like that. The directions call for extra non-dairy creamer, but the recommended amount didn't seem to be enough, so the next batch, I just made it with soy milk (no particular reason for soy over regular: I just don't have regular on hand).
That recipe actually says there are two ways you can prepare this:
There are two ways to do this: throw just about everything in a pot of
water and simmer, then add the milk, tea and sweetener and brew for a
few minutes; or, let the spices soak overnight in the water then
simmer in the morning with your tea leaves and milk.
(emphasis mine)
Have you tried the latter? That way you still only have to heat things up once.
I'd be hesitant to boil milk with spices and then store it cold, reheating again. If you're using dairy milk, that is. If you're using anything other than non-fat (skim) milk, you'll get a "skin" on the top of the milk when you're boiling it - that's one of the classic signs of masala chai for me. But anyway, it becomes substantially less appetizing if it has time to cool into globules and is then reheated again. I'm not sure what problems, if any, you'd encounter using non-dairy milk like almond or soy.
You could dump the pre-ground spices into your brewed tea with milk and sugar, but the flavor profile will be a little different. Boiling the spices with the milk and tea gives everything time to meld nicely and provide a really smooth flavor blend. But I don't see any especially compelling reason that you couldn't do it.
I would like to point out, though, that boiling enough water for a travel mug's worth of tea doesn't take any more time to do on the stove than it does in my electric kettle. Adding milk shouldn't make too much difference; I'm willing to bet that after you get familiar with the routine, you can follow this recipe and still have it take 5-6 minutes. :)
Purists will insist that the spices must be boiled with the water, but those are the same people who would scoff at you adding cold milk to your tea in the first place. There's no reason why you can't, other than it might cool down the rest of your tea.
Best Answer
Frothed milk is not essential to Masala Chai, it's normally made with plain milk; the frothed-milk version is mostly a Western variation. But I assume you like it with that little extra. You might try using a milk frother, you can get them much cheaper than the deluxe model I've linked to here. If you're very particular about your frothed milk though, it seems from some quite detailed instructions I found, that a proper milk steaming attachment as found on espresso machines is the way to go. The author of the instructions states that “With a little care, you can create steamed milk that is velvety smooth like the texture of wet shaving cream. The bubbles will be so small that you can barely see them! This is the way it’s supposed to be, because this way, it will blend with the espresso, creating a harmony of the flavors instead of a dry, tasteless cap floating on top.” The same author provides instructions on how to make Masala Chai with or without frothed milk:
You may also want to take a look at the page titled “Milk Frother Tips” on coffee-makers-cafe.com, which gives a comparison between different methods of frothing milk. But note that that page also states you will get the best results with an espresso machine's steam wand: