Can I just add the coffee powder to the basket and let the the water vapour do the work or should I make use of a tamp same as with a professional Espresso machine?
The general idea is that tamping with moka pots is unnecessary/harmful/dangerous because of the excessive pressure this will cause (see Ivan's answer: https://coffee.stackexchange.com/a/489).
However, we usually compact the ground coffee a bit with a spoon by slightly tapping on the grounds while making sure that there is a flat surface. This tends to give a richer flavour if, for whatever reason, you do not fill the basket to the top. (E.g. if you want to prepare a smaller serving and you don't have a smaller pot.) This is not traditional tamping, but somewhat similar.
My hypothesis is that the reason for the improvement in flavor seems to be the longer extraction time: If the basket is only half full, I mostly tend to get underextracted, somewhat sour-ish coffee. Compacting the grounds a bit results in more resistance to the hot water and, thus, a longer contact time. (Not sure if that hypothesis is correct, but the result is easy to reproduce for me.)
I have used several types of Moka pots in the 25 years since I learned about them, and I can confirm that with tamping, my Moka pots have never exploded, or even triggered the pressure release valve once, even after a decade or more of use.
Unlike espresso machines, a Moka pot lifts the grinds with the water, rather than pressing them down into the basket they were tamped into, so maybe that is why tamping doesn't seem to make a huge difference in pressure/time.
I suspect the pressure valve on a moka pot may just be there for emergencies, like if a child in your household innocently plugs the stem of your moka pot with something!
Still, I do tamp my moka pot, because it seems to make slightly better coffee, when I've experimented. Possibly it just increases consistency. However it will probably depend on the specific coffee you are using and what flavour profile you like. I highly recommend some careful experiments with tamping, grind, and amount of coffee to find what you like best.
Actually, on the internet you will find this advice universally for moka pots, which all seems clearly wrong to me:
- do not tamp
- do not use espresso grind
- those are not safe because the pressure will be too high, you will explode your pot
- put hot water in your pot (not cold) or you will burn your coffee
For tamping, I followed what I learned from normal Italian family usage in Canada (not my family, but 3 friends' families who were from Italy) when I was a young adult in the 90's. All of them tamped with a spoon, and all of them used standard Lavazza ground coffee, which is an espresso grind, according to Lavazza.
From personal experience, I find I get the best results (for my taste and coffee blend) with my burr grinder set to nearly its finest setting, and tamping firmly.
(The "using cold water causes a burned coffee taste" advice, repeated over and over in online articles, just doesn't make any sense. Sorry, that has to be pure internet echo-chamber nonsense.)
I have found that with tamping down the coffee produces a stronger extraction. Theory being - whether right or wrong - that the water picks up more coffee and at a slower rate. Experimenting without tamping produced a gushing and diluted extraction, which was no good for my use. Also only taking the first couple of tablespoonfuls maximum, because any further extraction will, again be too weak.