Preheat your oven to 350 °F. Get out two baking sheets and set aside.
Beat the butter, peanut butter, and sugar in a large bowl with an electric mixer until light and fluffy. Blend in the egg completely, then mix in the vanilla.
Whisk together the flour, baking powder, and salt. Mix into the butter mixture until thoroughly combined.
Stir in the cereal until mixed throughout the dough.
Drop by tablespoonfuls of dough, 2 inches apart, onto baking sheets.
Bake for 8 to 9 minutes or until lightly browned and the edges are set.
Cool on the baking sheets for 5 minutes, then transfer to wire baking racks to cool completely.
Store in a closed container at room temperature for up to 5 days, or in the freezer for up to 6 months.
Notes
you can use another flaked granola cluster cereal instead of Honey Bunches
as most cookies, these are best slightly underbaked