Knead until a smooth, velvety consistency has been obtained. Leave to rest at room temperature for 5 minutes. Roll out the dough and place the margarine in the centre and fold the dough over on itself so that the margarine is completely enveloped. Roll out the dough and fold into four layers; repeat the rolling out and folding procedure for a total of two folds of four layers. Finally roll out the dough again to a thickness of about 4 millimetres and cut into triangle shapes. Roll up the triangles tightly and place on baking sheets, curving the ends to create the traditional croissant shape. Leave in a rising room at 28-30°C with a relative humidity of about 80% for 60-80 minutes. Glaze with beaten egg and bake at 190-200°C for about 20 minutes.