½ C + 1 T butter
Whisk in a large bowl:
Blend into the eggs and beat until thick, about 10 minutes:
½ C + 2 T white sugar
the melted lukewarm butter
a smidgen of salt
(¼ t vanilla or lemon essence)
1½ t grated lemon rind (just the yellow part, not any white part. Don't forget to wash and dry the lemon first.)
2 C white flour
Cover and refrigerate for at least 1 hour. Alternatively, you can freeze the dough in batches. Wrap each batch in plastic, then put in a ziplock freezer bag.
Preheat oven to 170C (325F).
Lightly flour a clean surface, your rolling pin, and the bottom of a cookie cutter. Roll dough into about ½ cm (¼ inch) thickness, cut with a cookie cutter. Place the cutouts on a thinly buttered sheet of parchment paper (or baking pan or cookie sheet.) Ball up the scraps and roll out again until you've used all the dough.
Spread the tops of cookie with egg yolk. Bake until golden at the edges, for 12-15 minutes. Cool for a minute on the sheet before moving them to a cooling rack.