This recipe makes the best croissants. Be sure to use real butter. If you don't, the recipe will not turn out. If it were simply a matter of taste I would say use whatever you want, but in this case you have to use real butter because of its baking properties. I prefer to use salted butter but you may use unsalted if you wish. The preparation time is just a guess because you never know how long it's going to take for them to rise. I usually let mine rise for a bare minimum of 4 hours. So you may want to keep that in mind if you plan on serving them at a certain time. Note: If you wish to measure the flour by weight rather than by volume, 2 7/8 cups of flour is approximately equal to 12.68 ounces or 359 grams.