In a large pot, bring sugar, corn syrup and water to a boil. Butter and line a 9x13 baking sheet and spread the cashews out over the pan.
Continue to boil until temperature reaches hard crack, about 300 degrees. Once it comes close to temperature, it’ll start to brown so stir occasionally to keep it from burning. As soon as it reaches temperature, remove from the heat.
Stir in butter, vanilla and baking soda.
Pour over cashews. Sprinkle coarse sea salt and crushed cashews over the top. Drizzle the top with melted white chocolate.
Let cool. To remove from the pan and break up the brittle, I twisted the pan slightly to get it to break.
Break it up into pieces and serve.