2 c. firmly packed light brown sugar
1/2 c. light corn syrup
1/2 tsp. cream of tartar
6 qts. fresh popped popcorn
2 sticks butter
1 tsp. butter flavored salt
1 tsp. baking soda
1 tsp. vanilla
1 tsp. butter flavoring

Combine sugar, syrup, butter, cream of tartar, and salt in large saucepan. Heat to boiling over medium high heat, stirring constantly. Heat to 260 degrees on candy thermometer then remove from heat. Quickly stir in soda thoroughly and add vanilla and butter flavorings working quickly. When mixed well, pour over popcorn in 9 x 12 inch (or larger) pan. Coat evenly stirring to coat all kernels. Bake at 200 degrees for 1 hour, stirring every 20 minutes. Turn out onto wax paper to cool. Store in airtight container.