In a saucepan over medium heat, melt 1/4 cup (4 tablespoons) of unsalted butter. Stir in the brown sugar, corn syrup, heavy cream, one egg, vanilla extract, walnuts, and salt. Cook for a few minutes, stirring occasionally, until the mixture thickens slightly. Remove from heat and let cool slightly.
1/4 cup unsalted butter, 1/2 cup brown sugar, 1/2 cup corn syrup, ¼ cup heavy cream, 2 large egg, 1 tsp vanilla extract, 1/4 tsp salt , 1 ½ cups walnuts