Chips-A-Ho! Cookies are a fictional brand of cookies. They are based on the real Chips Ahoy! cookies.
The cookies appear in "Casa Bonita", while Cartman is trying to fool Butters Stotch into thinking a meteor has turned South Park into a toxic wasteland in order to go to his favorite restaurant, Casa Bonita.
Kyle hadn't invited Eric as he owed Butters a birthday invite, and Cartman is never even the least bit respectful to Kyle. Cartman locks Butters into a refrigerator to wait out the week while the alleged "monsters" roam the earth in search of flesh. Eric gives Butters a box of the cookies to eat.