I never developed any skill at the piano. Despite my failings, I persisted for eight ear-shattering years of lessons. Truth be told, I was in it for the snacks -- both of my piano teachers rewarded my terrible playing with treats. Those lessons instilled more than an appreciation of music: a lifelong love of chocolate and toffee popcorn.
In a large pot, heat the oil over medium-high heat. When it is hot, add the popcorn kernels and cover the pot. Once the popcorn starts to pop, reduce the heat to medium. Hold the lid on the pot and shake the pot until the popping stops. Transfer the popped popcorn to a large bowl and discard any unpopped kernels. Add the pecans.
Butter two large rimmed baking sheets. In a medium-sized heavy-bottomed pot with a candy thermometer attached, heat the butter, sugar, salt, and 2 tablespoons water over medium heat, swirling the pot occasionally, until the butter has melted. Cook the mixture until the candy thermometer reads 300 degrees F. Then remove the pot from the heat and quickly stir in the vanilla. Be careful; it will spatter a bit. Stir in the baking soda.
Carefully pour the mixture over the popcorn, and immediately stir the popcorn well to coat it in the warm toffee. Spread the coated popcorn out on the prepared baking sheets, and sprinkle with salt. Let the popcorn stand until it is completely cool.
Transfer the chocolate to a double boiler or large heat-proof bowl set over a pot of barely simmering water. Melt the chocolate, stirring it occasionally. Line a rimmed baking sheet with parchment.
Carefully drop a few pieces of popcorn into the melted chocolate and flip it around with two forks. Lift the coated popcorn out, tap it against the side of the bowl to remove any excess chocolate, and transfer it to the parchment lined baking sheet. Repeat with half of the remaining popcorn. Transfer the chocolate-dipped popcorn to the fridge until set, about 20 minutes. Extra chocolate can be cooled, wrapped in plastic, and used again.
When the chocolate popcorn has set, toss it with the plain toffee popcorn in a large bowl, and serve. Store in an airtight container in the fridge for up to 2 days.