01 - Line a baking sheet with parchment paper or a silicone mat and set aside.
02 - Toast pecan halves in a dry skillet over medium heat for 3–4 minutes, stirring frequently, until fragrant. Allow to cool, then roughly chop.
03 - In a large saucepan, combine granulated sugar, light corn syrup, and water. Stir over medium heat until the sugar fully dissolves.
04 - Bring the mixture to a simmer and attach a candy thermometer. Without stirring, cook until the temperature reaches 300°F (hard crack stage), approximately 10–12 minutes.
05 - Remove from heat and immediately add the unsalted butter, vanilla extract, sea salt, baking soda, chopped pecans, and puffed quinoa. Stir quickly and thoroughly—the mixture will foam rapidly.
06 - Pour the hot mixture onto the prepared baking sheet. Use a spatula to spread it evenly to approximately 1/4-inch thickness.
07 - Sprinkle the surface with additional flaky sea salt while still hot. Allow to cool at room temperature for 30 minutes until fully set and hardened.
08 - Break the cooled brittle into 12 irregular pieces and serve immediately or store.