Mention MOOCs in email to potential PHD supervisor? I graduated from a top Russian university (computer science) with moderately high grades in 2013 and after 3 years of industry experience decided to pursue a PHD abroad (ideally, in Germany). I know exactly what topic I want to investigate, found a professor who had recently done research in this field and am now composing an email to him.

I got some useful pieces of advice here at SE:

How to write a Cover Letter for applying to a PhD programme

Optimal structure of cover letter for PhD application submitted directly to PI

How much detail to include in first email to potential PhD supervisor?

How brief I should be when contacting a professor for a PhD position for the first time?

But one question remains.

In fall 2014 I discovered Coursera and since then completed nearly 30 MOOCs, most of them being relevant to the topic I want to do research in. These courses, despite being undergraduate level, did expand my knowledge a lot and, honestly, gave me a taste of what a world-class higher education looks like. I consider completing these MOOCs a valuable achievement of mine, but do professors think so? I'm afraid that if I briefly mention "some courses on the Internet", it would seem unprofessional (there's a ton of crap on the web that calls itself "online courses"). But if I go into too much detail ("completed MOOC X from Princeton, MOOC Y from Stanford, ..."), it would be too long for the initial email. As I already know, the most important thing when making contact via email is to be brief.

Would you include such information in the first email at all? My concern is that both my undergradute research and my job are not directly (but, somehow) connected to the research topic I'm interested in (the topic is quite new, not much research exists there yet). MOOCs are exactly what gave me a broader perspective and inspired me to continue my education.

What is the proper way to write about it?
It is possible to be both brief and comprehensive.

Be brief in the main e-mail: completed X MOOCs from established institutes.

Refer to an appendix for a complete list.  In that case, if the potential supervisor cares at all, s/he can glance through the list to see if s/he is at all impressed.