Step 1

Add the sugar and cornstarch to a medium-sized pot. Mix them together and set the pot over medium heat.

Step 2

Add the milk and stir constantly until it comes to a boil. Continue stirring for 1 minute longer.

Step 3

The milk should be thick enough to coat the back of wooden spoon. Take the mixture off the heat.

Step 4

Beat the egg yolks. Whisk one tablespoon of the hot milk into the beaten egg yolks.

Step 5

Continue to whisk in the milk, tablespoon by tablespoon, until the egg mixture is very warm.

Step 6

Set the remaining pot of milk over medium heat and whisk in the warmed egg mixture. Bring the pudding to a boil while stirring constantly. Continue stirring for 1 minute longer.

Step 7

Take the pudding off the heat. Add the vanilla and the butter. Stir until the butter has melted.

Step 8

Strain the pudding through a fine mesh sieve.

Step 9

Add the strained pudding to a large bowl. Serve warm or cover with plastic film touching the pudding's surface and store in the refrigerator until the pudding has cooled.