Mix flour and 1 cup butter thoroughly. Stir in whipping cream and mix well. Chill for 1 hour.

Preheat the oven to 375 degrees F (190 degrees C).

Roll dough 1/8-inch thick on a lightly floured board. Cut into 1 1/2-inch rounds. Transfer to waxed paper heavily sprinkled with sugar, turning to coat both sides. Place on an un-greased baking sheet. Prick in 4 places with a fork.

Bake in the preheated oven for 7 to 9 minutes.

Meanwhile, make the filling: Blend 1/4 cup soft butter, confectioners' sugar, egg yolk, and vanilla.

Put two cooled cookies together with filling.