I second the bulletproof coffee. I started that with virgin coconut oil and ghee for health reasons before I planned to gain. I had way more energy in the mornings which lasted longer than the usual cuppa does, but the problem was (for me back then), I gained weight. Stuck with it anyway.
So when planning to gain, it's a win-win. Now that I am trying to gain, I use butter instead of ghee, preferably grass-fed unsalted. I also add a good dose of heavy cream.
3 years