Preheat your oven to 350°F (175°C).
Combine the all-purpose flour and brown sugar in a mixing bowl.
Cut in the unsalted butter until the mixture resembles coarse crumbs.
Press the crumb mixture into the bottom of a greased 13x9x2-inch baking pan.
Bake the shortbread crust in the preheated oven for 15 minutes.
Sprinkle chopped pecans and coconut flakes over the partially baked crust.
Mix sweetened condensed milk, Kahlúa and vanilla in a separate bowl.
Pour the mixture over the crust.
Bake at 350°F (175°C) for 25-30 minutes or until the filling is set.
While the bars are baking, melt caramels over medium-low heat in a small saucepan until melted and smooth.
Drizzle the caramel mixture over the baked filling to make a gooey caramel layer.
Sprinkle with semisweet baking chocolate on top.
Let the bars cool before cutting them into squares.