I've been using a homemade "meal replacement shake" to try and slow down my weight gain and maybe loose a few pounds.  Not what you're looking to do, but if used in addition to regular intake, this should help you out and it's a lot cheaper than most if not all store bought powders. 

https://teaspoonofspice.com/make-homemade-protein-powder/

For sweetener I add 1/2cup of Nesquick per batch. 

I like the taste, some might not like the oats.  Kinda like an oatmeal cookie...sorta.  I've been using a Cuisinart to process everything.  It won't make a powder, the oats stay a little gritty.  Maybe an actual blender would work better but some little gremlin ran off with my lid.  Even so, I like it.

I'm not into the "all natural" everything, but I kinda like that other than the Nesquick, everything is minimally processed.

I mix with water to minimize calories.  I would think you could mix it with chocolate milk to avoid the Nesquik and add more oomph to it.  Maybe?