In a large mixing bowl, whisk together the eggs and sugar until they turn a pale gold colour. Whisk in the flour and cornflour and set aside.
Place the milk and vanilla bean paste in a heavy-bottomed saucepan, bring to a gentle simmer, stirring frequently. Remove the pan from the heat and let cool for 30 seconds.
Slowly pour half of the hot milk onto the egg mixture, whisking all the time, then return the mixture to the remaining milk in the pan. It is important to slowly pour the hot milk onto the cold eggs before you return the mixture to the pan to prevent the eggs from scrambling.
Bring the mixture back to the boil and simmer for one minute, whisking continuously, or until smooth.
Pour the cream into a clean bowl and dust with icing sugar to prevent a skin forming. Cool as quickly as possible, by sitting the bowl of pastry cream in another larger bowl of ice water. When cooled, refrigerate until needed.