Here is the recipe. My mother got it from this lady over 40 years ago. She used to make it into a Christmas tree shape for the holidays and use green frosting)

Hungarian Butter Slices (Makes 6 circles)

1 1/2 cups butter (must use for best results)
4 cups sifted flour
1/2 tsp. Salt
1 cake compressed yeast or (1 pkg, dissolved in 1/4 cup water)
3 egg yolks
1/2 cup sour cream
1 tsp. Vanilla

Sift flour, salt add yeast if the compressed kind. Cut in the butter until mixture resembles fine crumbs. Add egg yolks and pkg yeast if used. Add the sour cream and vanilla. Use hands to mix into six balls. Place in the refrigerator while making the following:

Filling:

3 egg whites
1 cup granulated sugar
1 cup ground walnuts or black walnuts
1 tsp. Vanilla

Beat egg whites until stiff. Gradually add the sugar, fold in vanilla and walnuts. Sprinkle powdered sugar on pastry cloth or board. Roll each ball into a rectangle about 1/8-inch thick. Spread with the 1/6 the filling and roll as for jelly roll. Place open edge on the under side and place on lightly greased cookie sheet. Form into a circle or whatever design you wish. Make cuts in the roll about 3/4 the way through and carefully arrange the slices so that they are laying on their side with the roll side (filling) up.. Bake at 350 for 35 to 40 minutes.

When cool frost with the following:
1 cup powdered sugar
2 tsp butter
1 1/2 tbsp milk or fruit juice