In large shallow roasting pan combine popcorn and nuts. Place in 250°F oven while preparing the glaze. In heavy 2 quarts sauce pan stir brown sugar, corn syrup, margarine, and salt. Stirring constantly; bring to a boil over medium heat. Without stirring, boil 5 minutes. Remove from heat; stir in vanilla and baking soda. Pout over warm popcorn and nuts stirring to coat well. Bake in 250°F oven, stirring occasionally, 1 hour. Cool; break apart. Store in tightly coverfed container. Makes about 4 quarts.