Classic Chocolate Walnut Fudge

Combine sugar, corn syrup, half & half and butter in a kettle or pot and heat to boiling, stirring occasionally. When 230⁰F is reached, add chocolate liquor. Finish cooking to 235⁰F and remove from heat. Either immerse pot in iced water or gently pour out onto cooling surface. Add vanilla but do not mix in. Leave untouched until cooled to 110⁰F. Once cooled, mix/beat until sugars begin to crystallize; surface will turn from shiny to a matte sheen when this occurs. Add walnuts and immediately pour into parchment-lined 9 x 13-inch pan. If desired, reserve some walnuts to add to top.