Add the cornflour, sugar and egg yolks into a large mixing bowl and whisk until it turns creamy.
Add the double cream, milk and vanilla bean paste into a saucepan and place over a medium to high heat, bring it almost to the boil.
Pour the hot cream into the egg/sugar mix and whisk as you pour it in.
It will be very runny, so now return it to the saucepan and cook over a medium heat, constantly stirring until it thickens to your desired consistency.
If you are not using it straight away, place a layer of baking paper over the top to prevent it from forming a skin.
