First up, make the custard to give it plenty of time to cool down. Pop the egg yolks, caster sugar, plain flour and corn flour in a bowl and whisk together to make a smooth paste.

Pour the milk and Vanilla Paste into a saucepan and pop over a medium heat stirring until simmering. Pour half the hot milk mixture into the egg yolk mixture and whisk to combine. Pour back into the remaining milk mixture. Pop the pan back over a medium heat and continuously whisk until the mixture begins to bubble. As it bubbles it’ll thicken, continue to whisk until it is a thick consistency, then remove from the heat. - make sure your custard has thickened and boiled before removing from the heat as this will help it set. Pop in the butter and stir until it has melted into the custard.

Pour into a bowl and cover with cling film, ensuring the cling film touches the surface of the custard as this will prevent a skin from forming on the custard. Leave to cool in the fridge for about an hour.

Line 2 baking trays with baking parchment. In a mixing bowl, beat together the butter and sugar until creamed. Beat in the egg yolk and Vanilla Paste.

Sift the flour and Baking Powder on top and mix together to form a dough. Split the dough into 8 equal pieces and roll in a ball.

Pop the balls of dough spaced out on your prepared baking trays, and pop into the freezer to chill for 30 minutes.

Ten minutes before baking, preheat the oven to 190˚C/170˚C fan oven/gas mark 5. Bake the cookies for 12-15 minutes until lightly golden, they will still be slightly soft in the centre but will firm up as they cool. Once the cookies are baked leave to cool on the trays for 15 minutes before transferring to a wire rack.

Once your cookies are cooled and you are ready to serve. Remove your custard from the fridge and whisk to loosen. Either spoon or pipe a dollop of custard on top of each cookie. Pour the sugar onto a plate and dip the top of each cookie into the sugar so the custard is covered in sugar. – if you custard is too runny then just sprinkle the sugar on top. 

Use a blowtorch to toast the sugar on top of the cookies and create a lovely crunchy topping. Only decorate your cookies when you’re are ready to serve as they will loose their crunch after a while.