Make the shortbread crust by mixing the butter and sugar until smooth and creamy. Slowly beat in the flour until combined. Take two thirds of the shortbread dough and press it into an ungreased 13x9 pan.
For the filling, cook the condensed milk and chocolate chips in a saucepan on medium low heat. Stir often and once the chocolate is melted, remove from the heat. Stir in the pecans and vanilla.
Pour the fudge filling on top of the shortbread crust.
Take the remaining third of the shortbread dough and sprinkle it in various size crumbs across the fudge filling.