Grease a large baking sheet with sides and set aside.

Melt butter in a heavy bottomed pan.

Add sugar, corn syrup, and water as the butter starts to melt.

Bring the mixture to a boil, stirring continually. Do not scape the sides of the pan while stirring. But, do scrape the bottom of the pan as you continually stir.

When the mixture comes to a full boil, add the macadamia nuts.

Continue stirring and cooking using a candy thermometer.

When the brittle reaches 300 degrees, remove from the heat and pour onto prepared baking sheet.

Using the wooden spoon, quickly spread the macadamia nuts out in the toffee so they are mostly in one layer.

Allow brittle to cool completely.

Break up and store leftovers in an air-tight container.