Shell the shrimp (you should have about 12 oz/300 g of peeled shrimp), making sure to keep the shells.
In a saucepan, sauté the shallot in the butter. Add the shrimp shells and the water. Bring to the boil. Remove the pan from the heat and allow to cool. When slightly cooled, sieve the stock over a bowl, keeping the liquid and tossing the shells. Allow to cool completely. You should now have about 1 cup/250 g of stock.
For the roux , melt the butter in a thick-bottomed saucepan. Allow the butter to melt and turn frothy, but not brown. With a whisk, stir in the flour and allow to cook until the mixture goes golden and forms a paste that doesn't stick to the pan. Add the stock and milk to the pan bit by bit, stirring until the liquid is fully absorbed each time before adding more. Keep stirring.
Allow the ragout to cook for a few minutes until the flour is cooked. Taste to ensure that the ragout isn't floury, and remove the saucepan from the heat once the ragout has turned shiny.
Soak the gelatine sheets in a bowl of cold water for 5 minutes to soften, then remove and gently squeeze to remove any excess water. Now add the gelatine to the ragout mixture (which should be no warmer than 160 degrees F/70 degrees C).
Beat the egg yolks and cream and add this mixture to the ragout. Season to taste with salt, white pepper, cayenne pepper, and a few drops of tabasco sauce.
Add the shelled shrimp to the ragout, add the chopped parsley, and mix.
Cover the ragout with plastic wrap and allow to rest in the fridge overnight.
Using an ice cream scoop, make little ragout balls of about 2 oz/60 g each. Flour your work surface with the fine breadcrumbs and roll the little balls into small cigar shapes. The shrimp croquettes can be frozen for up to 2 months or used straight away.
To deep fry the croquettes, start by adding flour to a large bowl. Whisk a little of the egg whites into the flour, until combined. Now add the rest of the egg whites and whisk again until combined.
Make a mound of coarse bread crumbs on your work surface. Dip the croquettes in the egg white mixture and dredge through the coarse bread crumbs.
Heat oil in a deep fat fryer (or large pot) to 350 degrees F (180 degrees C). Fry the croquettes for about 3 minutes until golden and crispy.
Tips Making your own breadcrumbs are a great way to use up stale bread.
How to make fine and coarse bread crumbs:
You will need one loaf of sliced white bread.
Preheat the oven to 250 degrees F (120 degrees C).
Cut the crusts off the bread and arrange slices in a preheated oven. Allow to dry for 1 hour.
Remove from the oven and use a rolling pin or bottle to create coarse bread crumbs (or pulse in a food processor).
Now sieve the bread crumbs over a bowl. The bread crumbs in the bowl are fine bread crumbs, while the crumbs remaining in the sieve are coarse bread crumbs.
Grey shrimp is very common in the North Sea; so common, in fact, that the Dutch name for them is simply Hollandse garnalen (Dutch shrimp). The critters are also known as crangon crangon, brown shrimp, common shrimp, bay shrimp, sand shrimp and crevette grise . You can easily substitute these shrimp with whatever small shrimp or prawns are native to your area, or simply chop larger shrimp into smaller pieces.
I've had good results using already shelled grey shrimp and fancy bottled organic shrimp stock from my local healthfood store. Obviously, if at all possible, homemade stock is always preferable.
See Holtkamp demonstrate the recipe on www.foodtube.nl (in Dutch).