Ask the chef
Some recipes call for de-veining shrimp. When steamed shrimp are served in Chinese restaurants they come with the heads and shells on and obviously haven't had the black vein on the back removed. I rarely see it done in other Chinese dishes. Is it necessary? It's very time-consuming.
De-veining shrimp involves cutting a slit down the back and pulling out the long black vein, which is the shrimp's digestive tract. I do this only if the shrimp I'm cooking are particularly large. Larger shrimps, naturally enough, have larger digestive tracts and the stuff inside can be gritty, which can ruin the texture of a dish. Small shrimps don't seem to have the problem of grittiness.
You might also want to remove the vein for aesthetic reasons because you can sometimes see it through the flesh of the shrimp when it is cooked. I do this for dishes where the sauce is pale and doesn't hide the vein, as in a ceviche.
I made hollandaise sauce recently for eggs Benedict. The recipe called for whisking the sauce constantly while cooking it over a double boiler, then keeping it warm while making the rest of the dish. The sauce was fine when I first made it, but after a while it separated and the fat rose to the top. What went wrong?
It sounds like the sauce became too hot while sitting over the double boiler, so it curdled. If that happens, try whisking in a few spoonfuls of cold water to cool it down. That should also smooth it out, but if it doesn't, start again with a fresh egg yolk in a clean bowl. Whisk the yolk, then add the curdled hollandaise a little at a time and it should emulsify again into a smooth sauce. You would save a mayonnaise the same way.
The next time you need to keep a hollandaise warm, try this trick I read about in Cook's Illustrated. Rinse a Thermos flask with hot water then dry the interior well. Pour in the hollandaise then put the lid on the Thermos. The insulation will keep the sauce warm. Although the article doesn't mention this, you should use the sauce as soon as possible because the warm environment is also perfect for the growth of bacteria.
