Line a baking sheet with parchment and lightly grease it. Warm nuts on the sheet in a low oven.
Combine sugar, honey, and water in a heavy saucepan. Attach a candy thermometer.
Cook over medium heat without stirring until the syrup reaches 250°F. Swirl the pan if needed.
Continue cooking to 295°F, then stir in butter and fine salt. Return to 300°F (hard crack).
Remove from heat. Quickly mix in vanilla, then sprinkle in baking soda and stir until foamy and light.
Fold in warm nuts. Immediately pour onto the prepared sheet and spread thinly with spatulas.
Sprinkle flaky salt if using. Cool completely, then break into shards and store airtight.
Notes
Variation: Add a pinch of cinnamon or cayenne with the salt for a warm or spicy finish. Try swapping mixed nuts for all peanuts or cashews. Storage: Keep brittle in an airtight container at room temperature for up to 2 weeks. If it softens, chill for 10 minutes, then return to room temp to crisp up.This recipe is an original creation inspired by classic Honey Nut Brittle Bliss flavors. All ingredient ratios and instructions are independently developed.