In a sauce pan, combine brown sugar and corn starch. Stir in raisins, orange peel, orange juice, lemon peel, lemon juice, and water. Cook and stir over medium heat until thick and bubbly. Cook and stir 1 minute more. remove from heat, stir in walnuts. Fill a pastry-lined 23 cm pie plate with raisin mixture. Adjust lattice crust; flute edge. Cover edge of pie with foil. Bake at 190ºC or 20 minutes. Remove foil and bake about 20 more minutes or until crust is golden Pastry for Lattice Top Pie: In a mixing bowl stir together flour and salt. Cut in shortening until pieces are the size of small peas. Sprinkle 1 tablespoon of water over part of the mixture, gently toss with a fork. Push to side of bowl. Repeat until all is moistened. Form dough into a ball. Divide dough in half. Take half, on a lightly floured surface, flatten dough with hands. Roll dough from center to edge, forming a circle about 30 cm in diameter. Wrap pastry around rolling pin. Unroll onto a 23 cm pie plate. Ease pastry into pie plate, being careful not to stretch pastry. Trim pastry to 1 cm beyond edge of pie. When pie shell is full with filling, roll out other half of pie pastry. Cut pastry into 1 cm wide strips. Weave strips on top of filling to make a lattice crust. Press ends of strips into rim of crust. Fold bottom pastry over the lattice strips, seal and flute. Bake as directed in individual recipe.