Koicha is a very concentrated serving of Matcha. And I've heard it described as being almost paste like. While mine was not quite "paste" it was very thick and probably close to an Eggnog or Heavy cream in consistency.
But what amazes me is even though you often hear "You need a very good matcha to make good Koicha" or some variation, vendors still give information on how to make it with just about any matcha they send out.
Now some of you may have experienced this yourself, but even with the High grade matcha that I reviewed yesterday from Ippodo, which made very pleasant and delicious Usucha, but as Koicha it was excessively bitter, and there seemed to be hardly any sweetness to it at all.
So I dare say if you are to make Koicha, it might be best to really splurge on the highest quality you can find from a very reputable vendor.
But dare I say I am energized beyond belief, and I need to go find something to focus my energy on!
*Edit: I did some more reading, and I was probably still thin on the amount of matcha, but also when making Koicha it is typically prepared using the Chashaku instead of the chasen, and there should not be froth.