Step 1: Lightly coat the bottom and sides of a 9×13-inch rimmed baking sheet or glass dish with vegetable oil spray. Line with parchment paper, ensuring a 2-inch overhang on the long sides. Lightly spray the parchment paper as well.
Step 2: In a large saucepan, combine the heavy cream, granulated sugar, unsalted butter, and light corn syrup. Stir over high heat until the sugar has fully dissolved and the mixture begins to boil.
Step 3: Reduce the heat to medium-high and continue cooking, stirring occasionally, until the mixture reaches 248°F (120°C) on a candy thermometer, approximately 15 minutes.
Step 4: Immediately remove the saucepan from the heat. Stir in the kosher salt and pure vanilla extract until well combined.
Step 5: Carefully pour the hot caramel into the prepared baking dish. Working quickly, evenly sprinkle the top with cacao nibs and flaky sea salt, according to taste.
Step 6: Allow the caramel to set at room temperature, uncovered, for at least 8 hours or up to 24 hours.
Step 7: Once set, lift the caramel out using the parchment paper overhang and place it onto a cutting board. Slice into desired sizes (approximately 1×1¼ inches).
Step 8: Wrap each piece individually in wax paper, parchment, or cellophane for storage or gifting.
Notes
Use a larger saucepan than expected, as the cream will cause the mixture to bubble significantly.
Have all toppings ready before the caramel reaches temperature, as the final steps require quick execution.
Yield may vary depending on size of cuts.