Preheat oven to 220C/Gas 8.
1) Combine vegetable fat, flour and salt. Cut shortening into dry ingredients until pea-sized balls form. Add cold water and toss with fork until mixture holds together. Cover and chill. Roll out dough and place in 20-cm pie plate.
2) Place greaseproof paper over crust and line with pie beads or dry beans. Place in oven and bake for 15 minutes. Remove paper and pie beads or beans and continue to bake until crust is golden brown. Remove pie from oven and place paper and beads back in crust to stop crust shrinking as it cools.
3) Mix sugar, cornflour and salt in bowl. Set aside. In saucepan, place egg yolks, milk and vanilla pod (sliced lengthwise), mix well. Cook over medium heat, stirring occasionally. Remove vanilla pod and extract seeds, placing seeds and pod back into mixture. When mixture is hot (not boiling), sift in dry ingredients.
4) Continue to cook, stirring constantly until mixture thickens and bubbles. Lower heat slightly and continue to cook and stir for 3 minutes. Remove from heat and remove vanilla pods. Add butter and chocolate. Stir until melted. Add coconut. Cover with cling film and chill.
5) Place 190ml double cream in saucepan. Heat until steaming (approximately 70C). Pour over white chocolate. Whisk until all chocolate is melted. Cool to approximately 50C.
6) Place whipping cream mixture in mixing bowl. Beat on medium-high speed until cream starts to thicken. Increase speed to high and continue to beat until stiff peaks form. Add a large spoonful of whipping cream to chocolate. Fold chocolate mixture into whipped cream.
7) To assemble place chilled filling into baked pie shell and top with mousse. Decorate with toasted coconut. Serve