This whole series of "Burning Questions" posts originated as a somewhat amusing troll through the One Block West Restaurant web site server logs, to see what search phrases were bringing people to the web site. As I went through the logs, the search topics seemed to fall into several broad categories, each dealt with in a separate post in this series. This post deals with substituting one ingredient for another.
Demi-Glace Substitute. Demi-glace is highly reduced stock, so you can substitute stock for it, but you're going to have to reduce the stock to thicken it. It's probably best to make a big pot of stock one weekend and reduce it to about a fourth of its volume, then freeze it in ice cube trays. You can put the frozen cubes in a seal-top bag in the freezer and have them at your disposal at any time. No need to thaw them, just drop the frozen cubes directly into the pan. You could thicken stock with a starch such as corn, potato, or arrowroot, but you're not going to get the depth of flavor that demi-glace brings to the table.
Andouille Sausage Substitute. Andouille as we think of it here in the US is a firm sausage stuffed with chunks of pork shoulder and seasoned with a good helping of cayenne pepper. You could substitute tasso or a firm city ham such as Hormel Cure 81 and some cayenne. Tasso or ham would have the closest texture to andouille. Or you could substitute another smoked pork sausage such as kielbasa and some cayenne. Kielbasa's texture will be wrong because it is made from a ground forcemeat. Me, I'd just go to Comeaux's web site and order the real andouille. I've been buying from Ray Comeaux since the early 1990's.
Can You Substitute Clam Juice for Oyster Sauce? Not exactly. Oyster sauce is a thick soy-based sauce. Clam juice is a thin stock akin to fish fumet or fish stock. I'm not sure why you would need to substitute for oyster sauce because it seems to be stocked in most groceries. You could thicken soy sauce with a little corn starch or substitute some other kind of soy product such as bean paste.
Fish Stock Substitute. Easy. Bottled clam juice or steam some mussels and save the liquid.
Can I Use Long Grain White Rice in a Risotto? No, I wouldn't recommend substituting long-grain rice for one of the Italian short-grain rices in risotto. You're going to end up with a soggy, non-creamy mess.
Differences Between Italian Parsley and Cilantro. Visually, you can see that cilantro on the left has rounder lobes than Italian parsley on the right with its more pointed lobes. Generally, you cannot substitute one for the other: they have vastly different flavors, but you should never need to because they're both available in most grocery stores. If you are confused about them at the market, crush a leaf of each and smell them.
Replacement/Substitute for Pasilla. If I don't have pasillas in the pantry, I would use guajillos. The important thing to remember is that the pasilla is a fairly mild red chile, so you should substitute another mild red chile for it. You could use anchos, but they have a much deeper, richer, more chocolatey flavor. You might want to view my Chile Primer.
Substitute for Pimentón. Pimentón is a paprika from Spain made from peppers that have been dried over oak fires, giving the resulting product a truly smoky flavor. There is no good substitute for pimentón. You could use any paprika in a pinch, but the smoky component would be lacking.
Poblano Chile Substitute/Replacement. I use poblanos as tasty substitutes for Bell peppers in almost all cooked applications. I suppose you could go the other way and use Bell pepper, but Bell peppers are very vegetal where poblanos have a nice round chile flavor. For most applications, I would probably go with a mild green chile such as an Anaheim.
Red Yellow Onions Interchangeable. Yes they are in most applications, unless color is a factor in the dish.
Can You Use White Wine Vinegar Instead of Sherry Vinegar? Yes, but you will miss a bit of nuttiness in the sherry vinegar. Technically, sherry vinegar, like Champagne vinegar, like Chardonnay vinegar, is a white wine vinegar.
Substitute for Corvina. Corvina is a mild, white, firm fish with small flakes in the Drum family. I serve it at the restaurant in preference to the similar Grouper which is overfished. Any of the larger drums would be fine substitutes: Black Drum, Red Drum, etc. as well as all of the groupers. Striped Bass which we call Rockfish is also a great substitute.
Non-Pork Substitute for Prosciutto. For those of you who cannot eat pork, I suggest that you use a similarly cured beef called Bresaola. A similar Swiss product is called Bündnerfleisch. You may also see it labeled as beef prosciutto.