Grits

Grits were an American food made from cornmeal. (PROSE: The City of the Dead)

In 21st century New Orleans, the Eighth Doctor ate grits, crushed together with deep fried rice cakes and maple syrup. Anji Kapoor considered the grits the Doctor ate "appallingly white" and unappetising, made from an "inferior form of cornmeal." She didn't try any. (PROSE: The City of the Dead)

Whilst on board the Valiant, British Prime Minister Harold Saxon once offered President Arthur Coleman Winters grits in lieu of tea. Saxon said he didn't really know what grits were, but he intimated that they might make the American feel more at home. (TV: The Sound of Drums)

Behind the scenes
In the real world, grits made from ground corn are a staple food of Southern USA. Maple syrup is symbolic of Canada, deep frying of Scotland, and rice of China. The mix of racial stereotypes is likely the intended joke in The City of the Dead.