A battery, an inverter and a set of sockets in one box. For cooking, it is the component everything else depends on, and the one most often bought too small because the specification that matters is not the one on the front of the box.
Two numbers, and you need both. Capacity in watt-hours (Wh) is how much energy it holds. Output in watts (W) is how fast it can deliver it. A battery with plenty of the first and not enough of the second will simply refuse to run an induction hob, and no amount of waiting fixes that. A 2,000 W hob needs a power station rated to at least 2,000 W continuous, whatever its capacity.
Surge is a third number. Motors and magnetrons draw more at the instant they start than they do running. Power stations quote a surge figure alongside the continuous one, and a unit whose continuous rating only just covers your appliance may still cut out at switch-on.
Pure sine wave, not modified. Induction hobs and microwaves are fussy about waveform in a way that a phone charger is not. Cheaper inverters output a modified sine wave, and the failure is not always obvious: things run hot, run oddly, or work until they do not.
LiFePO4 rather than older lithium chemistries, if the choice is offered. More charge cycles, better behaviour when warm, and less concerning to keep in a van.
What size, in practice, is arithmetic rather than opinion, and it is worked through in power for cooking.