Put sugar, flour and salt in a small saucepan.

Slowly add milk and stir until smooth, bringing to a boil. (Make sure you stir constantly)

Once at boiling point, boil for 60 seconds

Pour a small amount of the liquid into the two egg yolks and stir.

Return yolks and liquid to the pan and stir.

When the mixture starts bubbling, remove from heat and add vanilla.

Place in refrigerator until firm.