Maple Toffee Sauce

Melt butter in a medium saucepan over medium heat. Add brown sugar and maple syrup; stir to combine. Bring to a boil and immediately reduce to a simmer; cook until sugar has melted and sauce has thickened, about 5 minutes. Add salt, vanilla, and heavy cream. Simmer, stirring occasionally, until thick, about 5 minutes. Keep warm until ready to use.