1 cup chopped strawberry licorice twists (such as Twizzlers®)
2 cups broken small pretzels
2 1/2 cups brown sugar
2 cups butter
1 cup light corn syrup
1 teaspoon cream of tartar
sea salt to taste
Line 2 large baking sheets with parchment paper. Measure baking soda and vanilla extract into separate small bowls; set aside.
Heat vegetable oil in a large saucepan; add popcorn, cover, and cook, shaking often, until fully popped, about 5 minutes. Transfer popcorn to a large roasting pan using a strainer or your hands, leaving unpopped kernels in the saucepan. Distribute chopped licorice and broken pretzels evenly over popcorn.
Bring the brown sugar, butter, corn syrup, and cream of tartar to a boil in a heavy pot, stirring constantly. Place a candy thermometer into the caramel mixture, and continue boiling, stirring constantly, until mixture reaches 265 degrees F (129 degrees C), about 10 minutes.
Remove caramel from heat. Stir vanilla and baking soda into the caramel; it will foam and rise slightly. Pour hot caramel over popcorn mixture, stirring gently to coat evenly. Spread the popcorn mixture loosely onto the prepared baking sheets. Season to taste with sea salt; set aside to cool, about 20 minutes.
Break popcorn mixture into chunks. Store in airtight bags or containers.