Add milk and vanilla into a pan. It's best to use a heavy bottom pan for this recipe to prevent your cream from burning.
Add your eggs and sugar into a bowl and whisk until pale and creamy.
Add the flour and whisk until smooth.
Put the pan of milk over medium heat, take off heat as soon as it starts to show bubbles from boiling (right before boiling is ideal).
Very slowly pour half of the mixture in to the egg, sugar and flour mixture, whisking the whole time. Add the remaining milk and whisk in well. Pour the mixture back into the pan.
Bring the mixture to a boil, whisking the entire time. Then keep boiling and whisking for 1 minute, take off heat and pour into a clean bowl.
Cover the bowl right away to prevent a skin from forming. Let it cool then store in the fridge until you're ready to use.
Pastry cream will stay good refrigerated for up to 3-5 days or in the freezer for up to 3 weeks.
