Line two baking sheets with parchment and set aside.
Preheat oven to 350°F
In a food processor (or plastic bag, smash with a rolling pin) pulse 2 cups of the Cap'n Crunch cereal until finely ground. Set aside in a bowl.
In the bowl of a stand mixer, fitted with the paddle attachment, beat together browned butter, brown sugar and granulated sugar until fluffy and pale in color.
Beat in vanilla, whole egg and egg yolk and continue beating until light and fluffy.
In a separate bowl, whisk together baking soda, salt, flour and finely ground Cap'n Crunch cereal.
Reduce mixer speed to low and beat in the flour mixture until just combined.