I would say putting up 15 kilos of muscle mass in 10-12 weeks is definitely possible
if you have the perfect diet, workout plan etc.
BUT you would not be able to keep them all after your cycle.
Rich Piana claims to cycle with 1cc test 1cc deca weekly,
gaining 10 kilos of muscle in the first 8 weeks of his cycle.
I'd go for either Winstrol or Masteron if I were you.
Source:
https://www.youtube.com/watch?v=EJOIHC4fxeI