Place flour and salt in a bowl.Cut 1 T butter into flour, Make a well in the center and add water.Stir to combine. Turn dough onto a working surface, preferably marble, and knead 10 minutes, adding very little flour if needed. Chill half an hour. Meanwhile, prepare margarine. Process margarine and 2 T flour to combine. Make an even 10 cm square plaque .Chill 20 minutes. Roll out dough into a 1 cm thick square. Place butter plaque in center and fold the sides over the butter to cover it and overlap a little.Press edges with rolling pin. Roll out dough to 3 cm thick. Fold in 3 like a letter. Roll out again and fold as before. Chil wrapped in film and covered with a damp clothl half hour. Repeat the previous procedures 3 times. You will have rolled and folded 6 times altogether. You may freeze it up to 6 monthsor keep it in the refrigerator for up to 3 days.