Ants in the butter

We have a rather large butter dish…almost brick size, holding half a kilo of that creamy, high-cholesterol stuff. And we have those mischievous ants that seem to like to get into everything. This morning hundreds were gorging themselves, unaware of the danger to their tiny hearts. My dilemma: how do you get them out? My miserness refused to throw the lot away. Trying to remove them with a knife would only embed them in the sticky stuff. Instead I wrapped the dish in a plastic bag, stuck it in the freeze, hoping to kill the creatures, and then extract their corpses from the outside layer when the butter thaws. Do you think it will work? Let me know if you have better suggestions.