I have to say that I sprayed them with some kind of anti-aphid spray
that I found in the cupboard!!

They are mostly gone but there are still a few hanging in there. I'm
going to wait a few days and see how the mint reacts to the treatment.
If there are still aphids on the mint, I'm going to cut off all leaves
(even the healthy ones) and the affected stems.

Just for you info... when I noticed the problem I immediately cut off
some clean stems and placed them in a glass full of water. The trick is
to wait a couple of weeks till white roots grow and I'll plant them
again

Max