Preheat oven to 350 degrees. Grease an 7 x 11 inch pan with cooking spray.
In a small bowl, mix together sugar and flour, and cut the 2/3 cup butter in with a butter knife. Keep cutting it in the mixture until it has formed evenly-sized crumbs.
Press the mixture into the bottom of the 7 x 11 inch pan, and bake for 18-20 minutes - until the edges start to turn a golden brown.
Remove from oven and set aside so it can cool completely, then increase the oven temperature to 400 degrees.
Place coconut on a baking sheet, spread thin. Place in the oven and bake for 2-3 minutes. Remove from oven, stir coconut, and then bake for an additional 2-3 minutes until it has started to brown. Watch it closely so it doesn't burn. Remove from oven and set aside.
Place 1 cup of chocolate chips in a small bowl. Microwave for 30 seconds, then remove and stir. Continue microwaving in 15 second intervals until chocolate chips are completely melted. Pour chocolate chips over shortbread mixture in the 7 x 11 pan, then let it cool completely.
In a sauce pan over medium heat, combine the 1/2 cup butter, brown sugar, corn syrup, and sweetened condensed milk. Bring to a boil, stirring constantly (you don't want the mixture to burn, so keep stirring). Continue stirring for 5 more minutes, then remove from heat and stir for an additional 2-3 minutes.
Combine coconut mixture and caramel mixture, then spread it evenly over the chocolate chip layer.
Melt the 2nd cup of chocolate chips just like the first, and then drizzle it over the top.
Let it cool completely, about 1-2 hours, and then serve.