If you are using Savoiardi biscuits then room temperature coffee is probably best for making sure the biscuits don't get too soggy. When I make tiramisu, I roll the biscuits quickly through a shallow saucer of strong coffee which doesn't stay hot for long.
I agree, however, that luke warm coffee just doesn't taste good. The volatile oils in coffee oxidise quickly and by the time it has cooled it will taste stale. Personally I substitute for a dark, non-creamy, coffee liqueur (Tia Maria works well).
I would also like to try using cold brewed coffee which, I'm told, has a different, sweeter flavour profile compared to normal brewed coffee.
Another experiment you could try is to cool the coffee as quickly as possible after brewing, say using a metal mixing bowl in an ice bath, to see if that helps reduce oxidisation. If you attempt this, then please report back.
If you are mixing coffee into the beaten egg white, then be sure to first mix it with the mascarpone which, I assume, you will fold into the egg whites. This way it won't deflate. I would use cold coffee for this, but warm or hot should be ok if it doesn't curdle the mascarpone.
Update: I've tried a variation on my suggestion to cool the coffee as quickly as possible by making, what is known as, Japanese iced coffee. This involves brewing the coffee directly over ice.
Normally a 1:1 ratio of liquid water to ice is used. I wanted it a bit stronger for tiramisu, so I periodically emptied out the brewed coffee so that it would be cold but not too dilute.
I'm very happy with the results. Even though I brewed the coffee a bit too far in advance, it was not stale 20 minutes later when I came to use it for the biscuits. The tiramisu was great too.
Yes Turkish coffee grind is finer than esspresso grind.
Grinders are typically one of two kinds: Blade grinders, or burr mill/grinders. For a consistent turkish coffee or esspresso grind, it's recommended to get a conical burr grinder they can produce the fine grind you need without heating up the coffee and losing flavor. Also, the better ones tend to not 'click' as you adjust the grind size. That way you can calibrate your grinder to the specific bean roast without making big jumps in grind size.
If you are going for the whole 8 oz, i'd recommend giving the grinder a break to cool down part way and prevent the grind from getting too hot and essentially roasting again.
Best Answer
The temperature at the time of serving doesn't matter.
The Ottomans knew how to enjoy life. Coffee was served on social occasions, which happened at a slow pace in that part of the world. The ottoman effendi would spend hours sitting there, smoking a nargileh, endlessly turning the beads of a rosary, and taking a sip of coffee now and then. Even though it is served in tiny cups (which don't hold as many sips as your typical US mug), it would cool down considerably until it was drunk.
Note that hot food is a cultural tradition typical of Western cuisine. Being hot is not a quality attribute of food in Turkish cuisine in general, many dishes are eaten at room temperature. Coffee is still preferred to be hot, but this requirement is viewed with a much more relaxed attitude than in the West. If the coffee has gotten cold, it is still considered good enough to be drunk to the end. Or rather to the sludge, you don't drink Turkish coffee to the end.