Combine the egg yolks, sugar and lemon zest. Whisking constantly, slowly add about ½ cup of the warm milk to the egg mixture. Add the egg mixture to the remaining milk in the saucepan and cook, stirring constantly with a wooden spoon, until the mixture thickens. Do not boil.
Remove the custard cream from the heat and add the vanilla. Strain through a fine-mesh sieve into a bowl. Stir occasionally.
Let the custard cool and cover with plastic wrap.
Chill until ready to use.
Combine the egg yolks, sugar and lemon zest. Whisking constantly, slowly add about ½ cup of the warm milk to the egg mixture. Add the egg mixture to the remaining milk in the saucepan and cook, stirring constantly with a wooden spoon, until the mixture thickens. Do not boil.
Remove the custard cream from the heat and add the vanilla. Strain through a fine-mesh sieve into a bowl. Stir occasionally.
Let the custard cool and cover with plastic wrap.
Chill until ready to use.
