In a large heavy pot with a lid, heat 3 Tbsp of oil to medium-high heat. Drop a kernel of popping corn into oil and once it sizzles, add 1/2 cup popping corn. Cover. Once you hear the first kernels starting to pop, lower the heat to medium and shake the pot often until the popping stops. Tip open the lid a few times during popping to allow steam to escape.
Pour popped corn into a large roasting pan.
Repeat with the other 3 Tbsp oil and 1/2 cup popping corn and pour into second roasting pan.
Preheat oven to 250 degrees and arrange racks to fit 2 roasting pans.
In a large heavy saucepan heat butter, brown sugar and corn syrup and stir until blended at medium heat. Add a pinch of salt and allow to boil for 5 minutes. Remove from the burner and stir in vanilla and baking soda. Mixture will foam up. Stir well and pour over one pan of popped corn. Mix caramel into popcorn gently.
Place in preheated oven.
Sprinkle dry cheese sauce mix over popcorn in second roasting pan. Stir to distribute as evenly as possible without breaking popcorn. Place in oven on second rack.
Remove each roasting pan every 15 minutes to stir. Coatings will distribute more evenly during this process.
Remove from oven after 1 hour to cool. Gently break up clumps of caramel corn while still warm.
Combine both roasting pans and gently stir/fold together once cool.