Place the flour and margarines into a large bowl and, using a knife or fork, mash the butter into the flour until you have fine breadcrumbsAdd the sugar and mix through if usingAdd the egg to the mix and bring together to form a dough. If you need to, add a tiny bit of cold water to bring it together. I didn't need to but it will depend on the flour you useWrap in cling film and chill for 20 minutes before using