Grease 20 x 20 cm (8 x 8-inch) or 22 x 22 cm (9 x 9-inch) metal baking pan. Line pan with foil; grease foil.
Crust: In a bowl, use fingertips to mix flour, brown sugar and butter until soft dough forms. Press dough firmly onto bottom of pan.
Bake crust for 10 minutes or so, until lightly browned.
Filling: In large bowl, whisk eggs with brown sugar, flour, vanilla and salt, just until blended. Stir in pecans, coconut and butterscotch chips. Pour filling over warm crust. Bake 20 to 25 minutes, until lightly browned around the edges and filling is set. Cool completely in pan on wire rack.
Topping: Drizzle with melted white and dark chocolate. Drizzle with caramel sauce. Cover and refrigerate for several hours.
When cold, transfer with foil to cutting board. Cut into 8 strips, then cut each strip crosswise into 8 squares.