Mix softened butter and margarine with sour cream until completely blended. Stir in flour to make dough. Chill dough in refrigerator until it is firm. Dough may also be frozen until ready to use. Divide dough into 4 even balls. Flour the rolling pin and surface liberally. Roll each ball of dough out into a rectangular shape about the size of a cookie sheet or smaller. Line one end of the dough with preserves, pecan, and coconut. Roll the dough lengthwise starting with the filled end until all the dough is rolled. Seal the ends of the dough and place the strudel roll on the cookie sheet with the rolled edge down. Bake the strudel in a preheated 350 degree oven for 25 minutes or until lightly browned. Turn off oven and leave in the oven for 5 to 10 more minutes. Let cool slightly and then sprinkle with powdered sugar.
Makes 4 strudels.
Recipe variations: Any preserve or pie filling can be used for the filling. An example might be apple pie filling with sugar and cinnamon sprinkled on the top. The dough can be frozen until you are ready to use it or the completed strudels can be frozen before baking them.