1. In a medium bowl, cream butter and 2/3 cup flour until combined. Divide this into 2 equal parts, then roll each half between 2 pieces waxed paper into a 6x12-inch sheet. Chill sheets in the refrigerator.
2. In a separate mixing bowl. mix 3 cups of flour with yeast and set aside.
3. Get a small saucepan and stir together milk, sugar and salt and place it over medium heat. Heat the mixture until warm.
4. Pour your milk mixture over your flour mixture and add 2 eggs and vanilla extract. Stir for about 3 minutes and knead in the remaining flour 1/2 cup at a time until dough becomes firm.
5. Cover your dough and let it rise at room temperature for about 30 minutes to one hour.
6. Cut your dough in half and roll each half into about 14 inch square. Place 1 sheet cold butter over each dough square off to one side, then fold dough over and pinch the edges together.
7. Roll again each piece to a rectangle about 20X12 inches in size.
8. Fold again each dough into thirds. Repeat rolling and folding one more time then wrap it in plastic and refrigerate for about 30 minutes.
9. Repeat folding process twice and again wrap and refrigerate for about 30 minutes.
10. Roll out the dough out to 1/4 inch thickness and cut dough into squares.