It was milk that went past soured to a stage similar to cottage cheese. The article below says it only occurs with unpasteurized milk but I threw away a quart of milk that that clabbered on me this morning.
http://en.wikipedia.org/wiki/Clabber_(food)
Clabber is a food produced by allowing
unpasteurized milk to turn sour at a specific
humidityand
temperature. Over time, the milk thickens or curdles into a
yogurt-like substance with a strong, sour flavor. In rural areas of the
Southern United States, it was commonly eaten for
breakfast with
brown sugar,
nutmeg,
cinnamon, or
molasses added. Some people also eat it with fruit or
black pepper and cream.
Clabber was brought to the South by the
Ulster Scots who settled in the
Appalachian Mountains. Clabber is still sometimes referred to as
bonny clabber (originally "bainne clábair", from Gaelic
bainne — milk, and
clábair — sour milk).
[1] Clabber passed into Scots and
Hiberno-English dialects meaning wet, gooey mud, though it is commonly used now in the noun form to refer to the food or in the verb form "to curdle". A German version is called Dickmilch (thick milk), a Scandinavian
filbunke. In France, a similar food made from cream is known as
crème fraîche.
Clabber was sometimes served with a specialized spoon. This is a serving utensil formed with the handle made at a 90 degree angle from the spoon bowl, to accommodate the manner in which clabber had to be ladled out of the container in which it formed.
With the rise of
pasteurization the making of clabber virtually stopped, except on farms that had easy access to unprocessed cow's milk. A somewhat similar food can be made from pasteurized milk by adding a couple of tablespoons of commercial
buttermilk or sour milk to a glass of milk.