Coat bottom and sides of foil roasting pan with non-stick spray and put popped corn in the pan, set aside.

In a 2 quart sauce pan slowly melt butter over medium high heat.

Stir in brown sugar, corn syrup and salt.

Bring to a boil stirring constantly.

When a rolling boil starts, boil for 5 minutes without stirring.

Remove from heat and add baking soda and vanilla.

Slowly pour foamy mixture over popped corn, mixing well.

Bake at 250 degrees for 1 hour, stirring every 15 minutes.

Remove from pan onto wax paper to spread out and cool.

Store in tightly sealed container.