In a saucepan mix half of the sugar with the milk and vanilla extract. If you have a vanilla bean, cut it in half longwise and scrape the seeds with the back of a paring knife. Place the seeds along with the bean in the pot with the milk.

Bring the pot to medium-high heat, mixing occasionally.

In a bowl, combine the rest of the sugar and the egg yolks with a hand whisk.

Add the cornstarch to the yolk mixture and combine.

Wait for the milk to boil. Remove the vanilla bean. Pour the boiling milk over the egg yolk mixture slowly, while mixing with a hand whisk.

Pour the mixture back into the same saucepan. Bring it to low heat and mix constantly, until the cream boils (it will thicken, and you will see large bubbles). Use a hand whisk.

Remove from the heat, and add the cold butter cut into cubes and mix well with a hand whisk or spatula.

To cool it down, place it in an ice water bath, stirring occasionally, until the cream is cold. Cover with plastic wrap and keep it in the fridge.