Preheat the oven to 350F. Line your pie plate with pastry and crimp the edges.
In a medium bowl, stir together the brown sugar, maple syrup, golden syrup, eggs, butter and salt. (Don’t worry about getting all the lumps of butter out.) Scatter the pecans and walnuts over the bottom of the shell and pour the mixture overtop.
Set on a rimmed baking sheet and bake for 50-60 minutes, until set. Cool completely before cutting.