Preparation Place large sheet of foil on work surface; butter foil. Combine nuts and next 3 ingredients in medium bowl. Stir sugar, 1/2 cup water, and corn syrup in medium saucepan over medium heat until sugar dissolves. Boil without stirring until syrup turns deep amber color, brushing down sides of pan with wet pastry brush and swirling pan occasionally, about 10 minutes. Remove caramel from heat. Immediately stir in nut mixture (caramel will bubble up). Pour caramel onto prepared foil; spread thinly. Cool brittle until hard; chop. DO AHEAD Can be made 1 week ahead. Store airtight at room temperature.
Preparation Place large sheet of foil on work surface; butter foil. Combine nuts and next 3 ingredients in medium bowl. Stir sugar, 1/2 cup water, and corn syrup in medium saucepan over medium heat until sugar dissolves. Boil without stirring until syrup turns deep amber color, brushing down sides of pan with wet pastry brush and swirling pan occasionally, about 10 minutes. Remove caramel from heat. Immediately stir in nut mixture (caramel will bubble up). Pour caramel onto prepared foil; spread thinly. Cool brittle until hard; chop. DO AHEAD Can be made 1 week ahead. Store airtight at room temperature.