Preheat oven to 350 degrees. Cut each biscuit into sections (anywhere from 4 to 8 ) and shake pieces in a bag containing a mixture of the 2/3 cup sugar and 1 tsp cinnamon. Place into a greased pan (casserole pan is fine). In a small saucepan, melt butter or margarine and brown sugar. Bring to a boil, stirring constantly until all sugar is dissolved. Remove from heat and stir in cinnamon and vanilla. Pour over biscuits. You might need to make another batch of the sauce if you want it really gooey. Bake for 35-40 minutes – until done in the middle.