How to Limit Current to a Hot Plate
Short answer: A canister of butane/propane gas contains a lot more energy that batteries, is lighter, cheaper, etc. Use a gas cooking burner for camping. 

Long answer:

Your inverter might not like such a large load with a triac to dim it, so please check its documentation to see if they say something about triac dimmers. If it sounds like it should be OK, try a heavy-duty dimmer rated for at least 1.5 kW. I suggest experimenting with 250W then 500W halogen lights first, to see how your inverter handles this load.