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depends on whether you want to heat them quickly or efficiency
Since your energy flow rate is limited by the equipment you have at hand, the fastest method is also the most efficient, and vice versa. The only thing which would alter that would be an efficiency difference between the method used to heat a batch of water and that used to reheat the mixture peas-in-water.
On the other hand, what kind of efficiency? An electric kettle is more thermally efficient than a gas hob, but my utility company is charging nearly 4 times as much for electricity as gas, so gas is more economically efficient.
gbj_tester-
I mean more, oh shit, everything else is ready and I forgot the peas, it seems quicker to kettle boil enough water to fill the pea pan then whack said pan full of boiled water on the biggest burner that doesn't blast fire round the sides. Little bit of water and proper timing would be more efficient cost wise.
snottyotter
Surely that depends on whether you want to heat them quickly or efficiency.