You need teeny tiny brown shrimp for this dish. I think that potted shrimp is a very, very British thing, and I’m not sure where else in the world you can get these little fellas. I’ve been doing some trawling around the net for info but I can’t work it out.
It doesn’t help that what we call shrimp the Americans call prawns and vice versa. But here’s an illustration. Teeny weeny shrimp in a half teaspoon.
These are the fellas you want. Preferably from Morecambe Bay if you can get your hands on them, as I read in this article that they are the best. After reading what a hard life it is making a living out of trawling for these I’m going to appreciate them even more.
My pack of prawns was 70g 
which made about half a cup’s worth…
I used 1/4 of the amount of butter recommended by Vincent Price (for it is in his Treasury of Great Recipes you can find this – something the Price’s liked to have after sampling it chez the Karloffs) and actually needed a tiny bit more to cover the shrimp. I used a big pinch of salt, a big pinch of mace and a small pinch of nutmeg.
It pleased me greatly that the shrimp fitted perfectly in my little Hastings fishy dish (Hastings is a very lovely, very fishy, seaside place on the South Coast of the UK)
and I’ve just had some on toast for my breakfast (the last of my homemade Pain de Mie bread)
It was yummy but next time I think I would go heavier on the spices.
Thank you Boris and Vincent…
Those are the tiniest shrimp I’ve ever seen! Not being a shrimp eater…I have no idea about US availability. Reminds me of the Sea Monkeys I had as a kid though… Once had a co-worker that passed out after a night of too many drinks…she awoke the next morning to discover that the empty glass of water on her night stand…was actually her pet Sea Monkey container…lol. Probably not as tasty as yours…
Ha hahahahahah! Sea Monkey hangover! My chum Heather once washed my contact lenses down the sink after a very drunken night because I’d put them in a shot glass…