I have recently purchased a food processor but it had no instruction booklet or recipes with it. Is there a general rule as far as order of ingredients and which tool to use. Is it the plastic blade or the one with the sharp metal blades?
We would suggest firstly that you try and obtain a copy of your food processor handbook as these books are important guides to the function and use of your particular processor, plus safety tips and other information. You may be able to find a copy on-line or contact the manufacturer with the model number and see if they can send a new one out.
Most cakes made with food processors are made using an "all in one" method, so the ingredients are put into the bowl of the processor at the same time and whizzed until evenly mixed into a cake batter. However there are some exceptions so you should always read the recipe carefully. Nigella's Easy Almond Cake recipe (from Domestic Goddess and on the NIgella website) needs the marzipan and sugar to be blended together until smooth, before adding the other ingredients. Also in Nigella's Coffee Walnut Cake recipe (from Kitchen) the walnuts need to be ground with the sugar before the other ingredients are added.
Generally the metal blade will be used for cakes and pastry. The plastic blade is somethimes called a dough blade and can be used for bread and pasta dough, though many people find the metal blade also works well for these. However you should reaslly refer to the manufacturer's handbook for definitive advice.