1) Preheat the oven to 200°F and line two half-sheet pans with parchment paper.
2) Pour the popped corn and pecans into a large bowl (at least 6 quarts), and set aside.
3) Set a large saucepan over medium-high heat; make sure it's large, as the syrup you're making will foam up. Add the maple syrup, butter, salt, and flavor and cook, stirring occasionally, until the mixture comes to a low boil.
4) Cook the mixture to 230°F, thread stage on a candy thermometer. To test this, allow a drop of the syrup to cool, then pull it between two fingers; if it forms a thread between your fingers, it's ready.
5) Remove the pan from the heat and add the baking soda. Stir thoroughly; the syrup will foam up.
6) Immediately (and carefully) pour the hot syrup over the popped corn and pecans, and stir until the corn is well coated.
7) Spread the hot caramel corn onto the two parchment-lined pans. Bake for 1 hour, switching the pans halfway through, and stirring every 15 minutes.
8) Remove the popcorn from the oven. It's a warm, sticky, sweet and crunchy treat straight from the oven. But if you're not serving it immediately, allow the popcorn to cool; break up any clumps, and store it airtight at room temperature for several days.
Yield: 15 to 20 cups.