To prepare the pastry for blind baking, rub the margarine into the flour until rough breadcrumbs in texture.
Add the sugar and rub in.
Using a table spoon of water at a time, mix the water into the flour mix and bring it all together to a dough.
Don't knead the pastry too much. If too sticky just sprinkle a little more flour until its dry and easily pliable. If too dry incorporate small amounts of water until the dough is formed.
Pastry should be soft, pliable and not sticky.
Place the pastry dough on a plate or in a small bowl, wrap it in greaseproof paper or clean tea towel/flannel, and place in the refrigerator for at least 30 minutes. Longer if possible.
Preheat oven to 190 Celsius/ 170 Fan/ Gas 5. Grease your pie dish.
Sprinkle some wholemeal flour onto your worktop, Roll out the chilled pastry until roughly about 3 mm thickness.
Lift the pastry by draping it around your roller and carefully place it on top of your pie dish. Using a little ball of the pastry excess nipped off at the edges, gently push the case into the pie dish. Don't worry if some pastry breaks as you lift it up just gently press it into the case and squish the pastry back together.
Using a knife, trim the overlapping pastry away. Take a piece of greaseproof paper slightly larger than your pie dish diameter and scrunch it up. Press this into the pie dish. Pour in your baking beans.
Bake for 25 minutes on the middle shelf.
Remove the pastry case from the oven. Careful pull the ends of the greaseproof paper together and funnel the beans back into their storage jar. Or leave to cool on the paper if your storage is plastic.
Using a fork prick the pastry base all over, turn the oven down to 160 F and place it back in the oven for 13 minutes (or longer depending on your oven), to bake until golden. If your pie crust/edges are already nice and golden, you could scrunch some tinfoil over the edges to avoid over baking. But I didn't do this.
Remove from the oven and set aside to cool.
To prepare the filling, add the custard powder and sugar to a saucepan. Add about 100 mls of the milk and mix to a smooth paste. If too thick pour in a little more milk and make sure any lumps are mixed out. Gradually add the rest of the milk and the pineapple juice, stirring to avoid any lumps.
Add the pineapple chunks. Bring to the boil over a low-medium heat, stirring frequently to avoid burning or lumps forming.
When boiling, turn the heat down to low and gently simmer for 2- 3 minutes. Stir all the time. Custard will be nice and thick and should be coating the back of your spoon, but will still be able to be poured into your pie case. If you think your custard is overly thick just thin it up slightly by adding a little extra milk or pineapple juice and mix.
Pour and scrape the pineapple mix into the pie crust. Smooth the top. Leave to sit for an hour to cool before placing into the refrigerator for at least a few hours to set.
Enjoy! Serve with some vegan whipped cream if liked.