Rhubarb & custard slab pie - Good Food Middle East

Ingredients

• 600g plain flour?
• 150g icing sugar
• 300g cold butter, cut into small pieces
• 3 egg yolks, plus 1 egg, beaten
• 75g instant custard powder (we used Bird’s)
• 200g caster sugar, plus 1 tbsp
• 550ml whole milk
• 2 tsp vanilla bean paste, extract or 1 vanilla pod, seeds scraped out
• 700g forced rhubarb, ends trimmed and cut into 2cm pieces
• 1 tbsp cornflour