Set the oven to 350°F before beginning the dough. Let it reach temperature so the cookies start baking in consistent heat.

Work the butter and both sugars together in a large mixing bowl until creamy. The mixture should look evenly blended and slightly lighter, with no separate lumps of butter.

Mix the egg, vanilla, baking powder, baking soda, and salt into the butter mixture. Scrape through the bowl as needed until the mixture looks uniform.

Stir in the flour, stopping as soon as it disappears into the dough. The dough should hold together without visible dry patches.

Use a large spoon to fold the chocolate chips and Rice Krispies cereal through the dough. Lift dough from the bottom and turn it over gently until the additions look evenly distributed and the cereal pieces remain mostly intact.

Arrange roughly 2-tablespoon portions on a cookie sheet, fitting about 12 with room between them, press each slightly flatter, and bake for 8 to 9 minutes. Remove the sheet when the rims first show a faint light-brown color but the middles still look pale, soft, and unset.