1 pound (4 sticks) unsalted butter, plus extra for greasing pan
4 cups granulated sugar
1/2 cup light corn syrup
1/2 cup light rum
1 tablespoon vanilla extract
1 teaspoon fine sea salt
1 teaspoon baking soda
1 1/2 cups roasted, salted macadamia nuts, roughly chopped
1. Generously butter a large (13-by-18-inches) rimmed baking sheet.
2. Combine butter, sugar, syrup, rum, vanilla and salt in a 4-quart saucepan; bring to a boil over high heat. Insert candy thermometer.
3. Reduce heat to medium-high; cook, stirring constantly, to 300 degrees (hard crack stage), about 10 minutes.
4. Remove pan from heat; add baking soda and nuts, stirring vigorously (but carefully) to incorporate.
5. Pour hot mixture onto the prepared baking sheet, spreading evenly; cool completely, then break into bite-size pieces. Store toffee, layered with parchment or wax paper, in an airtight container at room temperature up to 1 week. It will last 2 to 3 weeks in the refrigerator; bring it to room temperature before serving.
-- Liz Gutman and Jen King, "The Liddabit Sweets Candy Cookbook" (Workman Publishing, $17.95, 302 pages)