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 to 4 minutes, stirring frequently, until fragrant and lightly browned. Let cool, then roughly chop.
03 - In a large saucepan, combine granulated sugar, light corn syrup, and water. Stir continuously over medium heat until the sugar fully dissolves.
04 - Bring the mixture to a simmer and attach a candy thermometer. Stop stirring and cook until the temperature reaches 300°F (hard crack stage), approximately 10 to 12 minutes.
05 - Remove the saucepan from heat. Immediately add the unsalted butter, vanilla extract, sea salt, baking soda, chopped pecans, and puffed quinoa. Stir quickly and thoroughly—the mixture will foam and expand.
06 - Pour the hot mixture onto the prepared baking sheet. Use a heatproof spatula to spread it evenly to about 1/4-inch thickness, working quickly before it sets.
07 - Sprinkle the surface with additional flaky sea salt while still hot. Allow to cool at room temperature for 30 minutes until fully hardened and set.
08 - Once completely cooled and firm, break the brittle into 12 irregular pieces by hand or by tapping with a knife handle. Serve immediately or store for later.