Blancmange is a dessert that appears in the episode "Squid's Visit."
It is a hot pink jello type of dessert with light pink frosting and there is also a cherry on the top of it. The color varies between the jelly body to the creamy top, the bottom being a darker pink while the top is a slightly lighter pink.
Role in episode
SpongeBob offers a plate of blancmange to Squidward after suggesting many desserts to make him comfortable and welcoming to his house, but the latter refuses to eat it. The reason Squidward denies this treat is because his vacuum cleaner is at stake.
Blancmange in real life is normally white.
Squidward says he does not know what it is. If SpongeBob copied Squidward's house, then that means Squidward had it in his refrigerator, meaning it is impossible that he would not know what it is.
Although, it's possible that all meals that SpongeBob offered to Squidward were not copied from Squidward's house, rather the meals were bought by SpongeBob.