For Dry Sandstone Squares Mix, COMBINE all ingredients in a clear 2-quart container with a tight-fitting lid. COVER with lid. STORE in a cool dry place until ready to give as a gift.
To make squares, PREHEAT oven to 350°F. SPRAY a 13 x 9-inch baking pan with cooking spray; SET aside.
PLACE 1 container dry mix in a large mixing bowl. STIR in melted butter until combined.
ADD eggs, one at a time, beating until combined after each addition. STIR in vanilla until blended. POUR mixture into prepared pan.
BAKE 30 to 35 minutes or until wooden pick inserted in center comes out clean. COOL completely in pan on wire rack. CUT into squares.
Dry mix can be prepared and held in container up to 2 weeks before giving as a gift.
Store baked squares, covered, in a cool dry place up to 2 days.