Butter Streusel

Ingredients 1/8 teaspoon ground cinnamon 1 cup pure maple syrup, plus more for serving 5 Granny Smith apples peeled, cored and sliced 1/2 inch thick 1/2 cup plus 2 tablespoons all purpose flour 7 tablespoons unsalted butter 1/4 cup walnuts, finely chopped 2 tablespoons dark brown sugar 1 vanilla bean, split and scraped 1/2 teaspoon…