Dissolve the yeast in the ¼ cup lukewarm milk, making certain that the milk is not too warm.
Stir in 1 tablespoon of sugar and set aside.
In a deep mixing bowl, combine the butter, remaining sugar, salt and scalded milk, and stir until all are blended.
When lukewarm, stir in the yeast.
Add the eggs and about 2 cups of the flour and beat to a smooth batter. Add remaining flour to make a tender dough.
Turn out on a floured board and knead for about 2 minutes.
Grease a large mixing bowl, grease the whole surface of the large ball of dough and place dough in a bowl. Cover.
Let rise in a warm, not hot, place to double its bulk (Takes from 2-4 hours).
Again knead on a floured board for about a minute.
Roll out ⅛ of an inch thick, Cut into3- to 4- inch circles. Place about a teaspoon of filling on each.
To shape true hamantaschen, pinch edges of the circle together over the filling.
Then fold over the flap and pinch these edges firmly together.
Arrange well apart on a greased cooky sheet.
Cover with a cloth and let rise again in a warm place to double in bulk.
Brush tops with the egg yolk, thinned with a little water (to make it easier to apply).
Bake in a moderate oven (350°) for15-20 minutes.
Brush with simple sugar syrup to make shiny and keep them fresh.