1. Prepare your workstation by lining a rimmed baking sheet with parchment paper or lightly buttered aluminum foil, and grease a wooden spoon or silicone spatula. Gather all ingredients and tools to ensure a smooth process.

2. Heat the sugar mixture by combining 1 cup granulated sugar, ½ cup water, and ½ cup light corn syrup in a medium saucepan over medium heat. Stir occasionally until the sugar is fully dissolved. Attach a candy thermometer and stop stirring, allowing the mixture to boil gently.

3. Add 3 tablespoons of butter (cubed) to the golden brown sugar mixture. Let the butter melt completely, incorporated into the mix for a rich consistency. Continue heating until the mixture reaches 270-290°F (soft crack stage) or 300°F (hard crack stage), as indicated by the candy thermometer.

4. Incorporate 1 cup of roasted and salted cashews into the sugar mixture once it reaches 290-300°F. Stir quickly and evenly to coat all cashews with the syrup.

5. Remove the saucepan from heat and immediately stir in ½ teaspoon of baking soda. Rapidly mix as the baking soda reacts, creating air bubbles for a lighter brittle texture. Add ½ teaspoon of vanilla extract for an aromatic finish, if desired.

6. Transfer the mixture onto your prepared baking sheet and spread it thinly and evenly using the greased spoon or spatula. Work quickly, as the brittle will harden almost immediately.

7. Allow the brittle to cool completely at room temperature. Once hardened, break it into smaller pieces using your hands or a mallet. For an extra touch, sprinkle flaky sea salt over the brittle before it sets.

8. Store the cooled brittle in an airtight container at room temperature to preserve its crunchiness and enjoy as a treat or gift.