Separate the eggs and beat the yolks with the salt and the sugar, until the mixture is thick and creamy. Beat in the cognac, very slowly and put the mixture into a double saucepan. Heat gently, whisking constantly until the advocaat is warm (not hot) and thick.
Remove the pan from the heat and stir in the vanilla essence. Pour into a jug. Advocaat is served in a glass and eaten with a teaspoon. It can also be topped with whipped cream.
Advocaat is nothing like the eggnog here in America. It is thick and creamy---not foamy at all.
This delicious Dutch drink is actually eaten with a spoon!