An Irish coffee is traditionally a strong sweetened (with muscovada or demerara sugar or syrup) coffee with a doubleshot of Whisky (I guess around 40-50ml for a glass of coffee of 150ml) and a layer of aerated cream on top of it.
- The coffee
I don't know what was used traditionally, I assume some kind of turkish coffee (or "Cowboy coffee"), where the grounds steep in water just of the boil for a few minutes or percolater coffee. Today I would probably use french press coffee or AeroPress with a metal disk instead of paper filter. You should keep in mind, that the coffee-sugar-whisky mix has to be higher in density than the slightly whipped cream. A pour over is likely too delicate (in taste and density). You also don't want coffee that's too strong (like espresso) because it would cover up most of the Whisky taste. Irish whisky tends to be lighter than Scotch or Bourbon. Add brown sugar to taste, but keep in mind that it is used to increase the density of the coffee-whisky mix as well, so one tablespoon should be added (for a glass of coffee as defined before).
Well it's called Irish coffee, so I would use Irish whisky. However I'm sure it's worth experimenting with different whiskys, trying to fit them to the flavor profile of the coffee. If you have a very nutty, chocolaty Brazilian coffee, maybe a smoky, spicy Bourbon fits better. I don't know much about whisky though. I'd just try different things. If you are afraid of too much alcohol evaporating, you could just wait until the coffee is cooled down to below 79°C. You can't drink it before that anyways, it would be too hot. After brewing, add sugar to cool it down, then I would wait until it's somewhere around 75°C, add the whisky, which will cool it down even further. Guessing to just below 70°C. Add cream and drink.
As said before, the cream should float on top without mixing with the coffee. Thus it has to be added after, which is usually done over the back of a spoon. It should be whipped lightly, but not too much either. You want it to be of a creamy, slightly aerated consistency. You drink the coffee through the cream.
Here is a link to a recipe similar to what I wrote, although theirs has some twists like nutmeg in it.