Pre heat your oven to 200 f
Whisk the egg yolks with your flavoring in a small bowl and put aside.
Now in a larger bowl mix the egg yolks, sugar and butter and put aside.
Now add the flour, baking soda and cream of tartar and mix into a large ball. Then let rest in the fridge for 1 hour or until ready to bake.
Put on awakening sheet in small walnut sized balls and cook for 8 minutes
If your mixture is to heavy or crumby then add milk, double-cream, creme fresh or if you don't have any, whipped cream. yes I tried it and it works just the same.