In a bowl, whisk the egg yolks until they're blended. Keep it aside.

In a sauce pan, warm the milk. Do not boil it.

Add flour, sugar, salt and butter to the milk and mix properly.

Warm the milk for a few more minutes and remember to stir constantly.

Once done, switch off the heat and start pouring the milk mixture to the egg yolk(that we had whisked earlier).

As you pour the milk mixture in the egg yolk, you need to keep stirring or else, the egg yolk might scramble.

Once you are done mixing the entire mixture to egg yolk, add vanilla extract and orange zest to it and mix it again.

Arrange 4 ramekin in a baking pan and grease them with some butter.

Pour the mixture in the ramekin and bake it at 350F pre-heated oven for about 45 minutes.