Cut butter and margarine into flour. Process a few seconds until mixture resembles coarse meal. Drop by drop add the water, processing very briefly. The whole process would take 20 to 30 seconds. Wrap and chill the pastry for at least 1 hour.If pastry has been chilled for a long time, let it sit at room temperature for at least 15 minutes before rolling.Lightly flour a pastry board, marble counter, or kitchen counter. Divide the pastry in half. Pat each piece of pastry into a flat round. Lightly flour the rolling pin.
Roll pastry in one direction only, turning pastry continually to prevent it from sticking to the surface.Using pie plate as a guide, measure rolled-out pastry — it should be slightly larger than the pie plate and 1/8-inch thick. Fold rolled pastry circle in half so you can lift it more easily. Unfold, gently fitting the pastry into the pie plate, allowing pastry to hang evenly over the edge. Do not trim the pastry yet.Fill the pie with filling. Then roll out the second crust in the same manner as for the bottom. Fold circle in half and with a sharp, pointed knife or small cutter, cut little vents in a decorative pattern.
Place folded pastry on one half the pie. Unfold, pressing top and bottom pastry together. Trim edges with scissors, leaving a ½-inch overhang. Fold bottom pastry overhang over top and press firmly to seal. Crimp rim, using fingers or the tines of a fork.
