What worked for me this year was:
-Big endurance base. Not recovery miles, but not too much into the tempo range. This was during a weight loss phase, but I was surprised at how well it prepared me for a solid build phase. I did this for about 6 weeks.
-SST: started off with 5 or 6 per week. Mostly steady SST, hard tempo. Some paceline rotation or terrain driven SST thrown in there.
-Friel Pace intervals (Same Time Until Can't Improve - STUCI): after 6 weeks of pure SST, I started throwing these in. I did these for about 6 weeks with the SST.
So, coming out of the endurance work, I felt like I should be weak, but I was really riding strong. My body responed rapidly to the SST and FTP shot up from 330 to 345 quickly. Then the STUCI put the finishing touch on and I was at 360W FTP.