Put the milk, heavy cream, and vanilla paste into a saucepan and heat it on medium heat until it comes to a simmer.
In a bowl, whisk the egg yolks and granulated sugar until it turns pale yellow. Whisk in the greek yogurt, flour, corn starch, and lemon zest until it becomes smooth.
Add the warm milk and cream mixture little by little to the egg mixture while constantly stirring.
Once all of the milk and cream have been added to the eggs, pour the whole thing back into the saucepan and heat it on medium heat while constantly stirring.
When the mixture begins to boil, cook for another 3 minutes. Pour into a bowl and let it cool in the refrigerator.