How to Make It
Preheat the oven to 350°. Line a 15- by 17-inch shallow baking pan with foil and brush the foil with butter. Line the pan with parchment paper and brush the paper with butter. Arrange a layer of matzo in the pan, breaking it to fit.
In a medium saucepan, melt the 2 sticks of butter with the brown sugar over moderate heat. Bring to a boil and cook, whisking the toffee constantly, for 5 minutes. Pour the toffee evenly over the matzo and spread it in a thin layer. Transfer the pan to the oven and bake for 5 to 8 minutes, or until bubbling.
Remove the toffee matzo from the oven and sprinkle the chocolate chips on top. Let the chocolate melt for 5 minutes, then, using an offset spatula, spread it evenly in a thin layer. Sprinkle the nuts on top and season lightly with salt. Let cool to room temperature, or refrigerate for faster cooling. Break the toffee into pieces and serve.