I was also happy to find out that the potato is a COMPLETE source of protein. I think the high glycemic load of white potatoes is overhyped and I've yet to see my triglycerides go up yet.
As for the workout, might I suggest doing a big 3 workout.
3 sets of 20 reps circuit of 3 major exercises. As long as you use a good weight at maybe 40% max you should feel it at the end of the workout for sure!
This is a crossfit routine I saw on youtube somewhere...
Do one circuit with minimal rest in between each exercise, then wait 2 minutes for glycogen repletion.
If you do it right, your time (plus warmup) should be 25 minutes.