Preheat the oven to 190ºC . In a bowl with an electric mixer cream the butter with the brown sugar until the mixture is light and fluffy and beat in the egg yolk mixture or the egg white. Add the flour, the baking powder, the salt, and the vanilla, stirring until the dough is blended well, and stir in the chips and the cereal. Arrange level tablespoons of the dough 5 cm apart on a lightly greased baking sheet and bake the cookies in the middle of the oven for 8-10 minutes, or until they are golden brown. Transfer the cookies with a spatula to a rack and let them cool.