Preheat oven to 325 and line an 8x8 or 9x9 pan with parchment paper lining the bottom and sides.

Cream together the 12 tbsp unsalted butter, softened slightly or cold, 6 tbsp brown sugar, and ½ tsp kosher salt on low speed to incorporate, then on medium speed for 2-3 minutes or until light and fluffy.

Add 1 ⅔ cup all-purpose flour and mix on low until flour is combined and dough has mostly come together--a few crumbly bits are okay. Press the dough evenly into the prepared pan, then dock all over with a fork. Bake for 25-30 minutes or until the edges are turning golden and the top looks matte.

With the oven still at 325, spread 9 oz sweetened, shredded coconut evenly onto a baking sheet. Bake for 10-12 minutes, stirring halfway, until coconut is golden. (Uneven browning is totally fine--just make sure no parts get scorched).

In a small saucepan, add 1 cup granulated sugar over medium heat. Let cook until the sugar starts to liquify around the edges. Stir occasionally to evenly distribute the un-melted sugar until the sugar has all melted into an amber syrup.

Add 6 tbsp unsalted butter, softened and whisk until incorporated--the mixture may sputter, but just keep whisking until it comes together. Finally, add ¼ cup heavy cream and whisk until fully combined. Let boil for 1 minute or until it reaches 220 F, then remove from heat and whisk in 1 tsp kosher salt.

Add the toasted coconut to a large mixing bowl. Pour the warm caramel over and fold together until well combined.

Spread the toasted coconut caramel mixture evenly on top of the shortbread crust (cooled or still slightly warm is fine). Chill for at least 20 minutes or overnight in the fridge to let mixture set.

When ready to serve, cut the shortbread into bars (I usually cut 21 bars in a 3x7 grid but you can even cut into smaller squares if you like). Melt 3 oz semisweet, milk or dark chocolate chips or bars and drizzle over the top. Finish with flaky salt if desired.