Preheat the oven to 350°F (175°C). Line a 9 x 13 inch baking dish with parchment paper.

Combine 1 3/4 cups all-purpose flour, 1/3 cup granulated sugar, and 1/2 teaspoon salt in a large mixing bowl.

Grate 3/4 cup plus 2 tablespoons cold unsalted butter into the flour mixture. Rub the butter into the dry ingredients with your hands until coarse crumbs form.

Transfer the crumb mixture to the lined baking dish. Press it into an even, compact crust using the bottom of a measuring cup.

Bake the crust for 15 minutes, until it is lightly golden around the edges. Remove the dish from the oven.

Melt the remaining 1/2 cup unsalted butter in a saucepan over medium heat. Cook while stirring until the butter smells nutty and brown flecks appear.

Remove the browned butter from the heat and stir in 1/2 cup granulated sugar, 1/2 cup brown sugar, and 1/4 teaspoon salt. Let the mixture cool for about 2 minutes.

Whisk 3 large eggs and 1 1/2 teaspoons vanilla extract into the browned butter mixture until smooth.

Stir 1 1/3 cups rolled oats, 1/2 cup shredded sweetened coconut, and 1 1/2 cups semisweet chocolate chips into the topping mixture.

Spread the topping evenly over the partially baked shortbread crust. Smooth the surface with a spatula.

Bake for 15 to 20 minutes, until the topping is set and the surface is golden brown. Remove the bars from the oven.

Sprinkle the warm bars with coarse salt and the remaining 1/4 cup semisweet chocolate chips. Let the bars cool on a wire rack.

Refrigerate the cooled bars until cold and firm, about 60 minutes. Cut into 16 bars and bring to room temperature before serving.

Cool and refrigerate until cold before cutting.

Allow bars to come back to room temp for serving.