Cook the Book: Salted Caramel and Walnut Slice

Name: Cook the Book: Salted Caramel and Walnut Slice
Ingredients: For the shortbread base:; 1 cup all-purpose flour; 1⁄2 cup light brown sugar; 1⁄2 cup walnuts, finely ground; 1⁄4 cup unsweetened dried coconut; Pinch of salt; 1⁄2 cup (1 stick) unsalted butter, melted; 1⁄2 teaspoon vanilla extract; For the caramel filling:; 1⁄4 cup honey; 2 tablespoons unsalted butter; One 14-ounce can sweetened condensed milk; 1⁄4 teaspoon salt; For the chocolate topping:; 6 ounces bittersweet chocolate, broken into pieces; 1 tablespoon unsalted butter; 1 tablespoon vegetable oil; Flaky sea salt