Preheat oven to 350°F. Line a baking sheet pan with parchment paper or a silicone baking mat.
Place butter in a small saucepan over medium-low heat.
Once the butter is melted, continue to cook stirring constantly until the butter turns a light golden-brown color. Remove from the heat immediately and pour into a large mixing bowl.
Add light brown sugar and granulated sugar to the brown butter. Stir until combined and smooth.
Add egg and vanilla extract and mix well until smooth.
Add all-purpose flour, baking soda, and salt. Mix until the dry ingredients are well combined and the mixture forms a dough.
Fold in the chocolate chips, toasted coconut, and crisped rice cereal until well dispersed throughout the cookie dough.
Portion the dough into balls using a large cookie scoop (3 tbsp). Place the cookie dough balls onto the prepared baking sheet pan. Allow room for spreading.
Bake the cookies for 10 to 12 minutes. The cookies will appear underdone. Remove the pan from the oven and allow the cookies to cool on the pan for 2 minutes. Transfer the cookies to a wire rack to cool to room temperature.