Preheat oven to 350º. Lightly grease a 9 × 9-inch baking pan, or line it with parchment paper or non-stick foil.

Process flour, sugar, and butter in a food processor until it forms fine crumbs. Pour the crumbs into the prepared pan and press into an even layer.

Bake for 15 minutes, until the base is set and the edges are lightly browned. Cool completely on a wire rack before topping.

Place the caramels in a microwave-safe bowl with the water and butter, starting and stopping to stir every 30 seconds. When smooth, fold in 1 ½ cups of the toasted coconut with a spatula.

Put spoonfuls of the topping all over the shortbread base. Using an offset spatula, spread the topping into an even layer. Sprinkle with the remaining coconut and gently press into bars. Let topping set until cooled.

Use the foil or parchment to assist in moving the bars to a cutting board. Cut bars into 16 squares. In a medium bowl, gently melt together the chocolate chips and oil in the microwave. Stop to stir frequently until almost completely melted. Let the residual heat finish the melting process.

Line a baking sheet with parchment. Remove less than half the chocolate to a piping bag or a quart Ziploc bag for the final drizzle, and set aside.

Dip the bottoms of the bars into the chocolate, removing excess on the side of the bowl, then place on the baking sheet to firm up. Repeat with all bars.

Drizzle each bar with the remaining chocolate using a piping bag or Ziploc bag with the corner snipped off.

Allow chocolate to cool and firm up before serving.