For the Cookie Crust:
- 125g unsalted butter, at room temperature, divided
- 75g brown sugar, divided
- 30g caster sugar
- 1 large, free range egg
- 100g rolled oats
- 70g plain flour
- 1/4tsp baking powder
- 1/4tsp bicarbonate of soda
- 1/4tsp fine salt
For the Filling:
- 150g caster sugar
- 100g brown sugar
- 1tbsp skimmed milk powder
- 25g cornflour
- 100g unsalted butter, melted
- 100ml whipping cream
- 4 large, free range egg yolks
- 1tsp vanilla extract
Preheat oven to 175°c. Line 13×9″ baking tray with parchment. Combine 85g of the butter, 60g brown sugar, and the caster sugar in the bowl of an electric mixer. With the speed on medium low beat the mixture until light and fluffy, scraping down the sides of the bowl as you go. Add the egg and beat until pale and fluffy. Add in the oats, flour, baking powder, baking soda, and salt and beat until well incorporated. Turn the cookie dough out onto the prepared baking tray and press out evenly to edges of the pan. Bake until golden, around 20 minutes. Cool completely
Crumble the cooled cookie into the bowl of a food processor, add the remaining 40g butter and 15g brown sugar and pulse until the mixture sticks together in your fingers. Turn the dough out into a 9″ pie plate and press it evenly onto the bottom and up the sides of the plate. It’s almost impossible to make this look neat so don’t worry if it looks a bit rustic.
To make the filling mix the sugars, cornflour and milk powder together in a medium bowl until well blended. Add the melted butter, whipping cream, egg yolks and vanilla extract and mix until there are no lumps and the filling is smooth.
Place the pie crust onto a baking tray and pour the filling into the crust. Bake the pie for 30 minutes at 175°c then reduce the temperature to 125°c and bake for a further 20 minutes. You want the filling to be just about set round the edges but still jiggles in the centre. Allow to cool to room temperature before transferring to the fridge to chill overnight.
To serve dust the top of the pie with icing sugar.
If your pie isn’t quite set after the 20 minutes at 125°c just keep checking on it every 5 minutes until it’s ready. Mine took around 30 minutes extra but every oven is different.
This pie keeps well covered in the fridge for up to 5 days, if it lasts that long!