another master's or PhD? Here is my situation, I have obtained a MSc in Computer Science in Europe with some publications in the field. Actually I would like to follow PhD studies, but the problem is that a lot of them are asking to have a proven track in Machine Learning (also in Europe). I have not followed any course on that topic and the things that I have learned about that field was from books, Coursera, or the Internet. I really like the field, but I regret that I did not follow any course beforehand, even though I know theoretically and practically the basics.

How I can address that in my PhD applications? or should I follow another MSc with specialization in Machine Learning?

Any suggestion?
Although it is odd for universities to ask you this, assuming that they did 
you have several options


Attend credit courses pertaining to Machine Learning or Artificial Intelligence and re apply
Get some industrial experience in those fields and re apply
Select a program that does not require Machine Learning background.
Talk to dept advisers telling them that you will attend these courses 
when you are admitted, probably get a conditional acceptance or 
you do not want to do PhD in machine learning fields but something else
(assuming that is the case) and approach the faculty member to back you up.