1. In a medium saucepan, combine the butter, brown sugar, maple syrup, and milk. Bring to a simmer, stirring occasionally. When it begins simmering, cook for 1 minute. Remove from the heat and stir in vanilla and finely chopped pecans.
2. Carefully pour the filling evenly over the crust, gently spreading with a rubber spatula so the pecans and liquid are evenly distributed.