On my desk right now is a big cookbook-Americanizing job. This particular title was one of the UK’s fastest-selling books of all time (whatever “fastest-selling” means), and the US publisher is probably expecting to do similar numbers here. No pressure. The main part of my assignment is to convert from metric to US measures—milliliters to cups or fluid ounces, grams to ounces and pounds, centimeters to inches, and in many cases weights to volume. (What’s the volume of 100 grams of frozen peas? I can tell you!) As always, one of the challenges of Americanizing is knowing how accurate is accurate enough, and how accurate is too accurate. When you’re making a soup, for example, the amount of broth doesn’t need to be expressed…