Combine 4 oz/110 g of the milk with 2½ oz/70 g of the sugar in a saucepan and bring to a boil, stirring gently with a wooden spoon.
Meanwhile, combine the flour with the remaining 2½ oz/70 g sugar. Stirring with a whisk, add the remaining 12 oz/340 g milk. Add the eggs and egg yolks, stirring with the whisk until the mixture is completely smooth.