How to Make It
Lightly butter a 9-by-13-inch metal baking pan and line with parchment paper, leaving a 1-inch overhang on all 4 sides.
In a small saucepan, bring the cream to a boil; remove from the heat. Add the tea bags, cover and let stand for 12 minutes. Gently squeeze the tea bags to release any cream, then discard. Stir in the vanilla and salt; keep warm.
In a medium, heavy- bottomed saucepan, cook the corn syrup over moderately high heat, swirling the pan occasionally, until it begins to bubble, 2 minutes. Sprinkle one-third of the sugar over the corn syrup and, using a small heatproof spatula, poke the sugar into the hot syrup until incorporated. Do not stir. Repeat with the remaining sugar in 2 batches, using a wet pastry brush to wash down any crystals on the side of the pan. Continue cooking over moderately high heat, swirling the pan occasionally, until a dark amber caramel forms and the temperature reaches 330° on a candy thermometer, about 15 minutes.
Remove the saucepan from the heat and gradually add the warm cream, whisking constantly, until incorporated. Add the 300 grams of butter in 2 batches, whisking until melted before adding more. Continue whisking the caramel vigorously until it is glossy and registers 190° on a candy thermometer, about 5 minutes. Fold in the pepitas.
Scrape the caramel into the prepared pan, then gently tap it on a work surface to release any air bubbles. Let stand at room temperature for at least 3 hours, cover loosely with foil and let stand overnight.
Invert the caramel onto a work surface, peel off the parchment paper and cut into 1-inch squares. Wrap each caramel in a square of cellophane and twist the ends to seal.