You should not be there in the first place. A lot must have gone wrong in your decision making to end up low, IIMC and above terrain that does not allow a safe precautionary landing, while moving towards high terrain.
Once in that predicament, climb at Vy to above MSA then level, get on your radio and call for vectors.
Any slower and you will have less rate of climb and an even more unstable aircraft. Any faster and you're eating up distance more than necessary while lowering your rate of climb.
Chances are though, you won't survive the climb if you're not accustomed to flying on instruments. And by that I mean more than the minimum exposure to flying the dials. The statistics are just not good.