Preheat oven to 350 degrees.

Layer the coconut on a rimmed baking sheet. Bake for 4 to 5 minutes, stirring occasionally, until light and golden brown. Be careful to not let the coconut burn.

Set aside to cool.

Keep or preheat the oven to 350 degrees.

Grease a 13 x 9 baking pan. Alternatively, you can layer 2 sheets of aluminum foil perpendicular to each other to make a foil sling (leaving extra foil hanging over the edges of the pan. Push foil down and smooth. Grease foil.

In a medium bowl, add the flour, baking powder and salt. Combine by stirring with a whisk.

In a separate medium bowl, add the brown sugar and melted butter. Stir with a whisk until combined. Whisk in the eggs and vanilla.

With a rubber spatula, fold in the flour mixture until just combined.

Add the semi-sweet chocolate chips, white chocolate chips, toasted coconut and nuts (if using). Gently fold in to evenly distribute through the batter.

Place the batter into the prepared baking pan. Make sure the top is even and smooth.

Bake for 22 to 25 minutes or until the top is shiny and cracked and is firm to touch. Rotate pan halfway through baking.

Allow the bars to cool for 2 hours. Cut into bars and serve. If using the foil sling, lift the bars from the pan and then cut into bars and serve.