I know that @Ann_Thas quite a bit of experience cooking with spot prawns and probably has some good suggestions.
Despite living near the docks and able to purchase spot prawns fresh most years, I rarely do. My husband really doesn't like them that much and so we only have them occasionally. When we get them fresh, we cook them right away - just steamed/poached/boiled, heads and all, maybe with some lemon zest, garlic, bay leaf. I know if we want to keep them, we need to remove the heads because of the enzymes.
https://skipperotto.com/live-spot-prawn/
Since yours are frozen @KennethT, I'm guessing the heads have already been removed?
We can get them in local stores, head removed, fresh or cooked but they tend to be pretty pricey.
I know that @Ann_T has purchased from Walcan and I see they have a short video on cooking them, but these are fresh and with heads:
https://shop.walcan.com/pages/recipes
More good info from Walcan:
https://shop.walcan.com/pages/bc-spot-prawns
