French people call these quenelles but most Americans might think of them as fish meatballs, or as fish-flavored matzo balls. So whatever. A way to make fish a little fancier.
How to make shrimp quenelles:
Put on a large pot of water to boil, and start a separate pot of rice on the side. Take half a pound of tiny cooked shrimp and mash them with the immersion blender. Add half a cup of thick drained yogurt, salt, pepper, and an egg white. You can whip the egg white or not. If the mixture is thick enough to form little balls, good. If not, add small amounts of flour until it gets that thick.
When the water boils, form little balls or logs out of the fish paste and drop them gently in the simmering water. Continue until the pan is crowded or all the fish is gone. Simmer until they float and turn over, about ten minutes. Remove gently with a slotted spoon.
Meanwhile, make the sauce. In a medium-size frying pan or small saucepan, melt 1/4 stick of butter. Add a half a cup of white wine. Then add half a cup of thick yogurt and the leftover egg yolk from the quenelles. Stir until it forms a sauce. Add a teaspoon or two of tomato paste, and stir again. Serve the quenelles over the rice, with the sauce on top.
Can I keep this for later?
Yes, but the quenelles will be denser and less tasty as leftovers.