i am making frosting for german chocolate cake and i forgot the evaporated milk!
Do you have whole milk? If you have a little time, though, you can easily reduce a quantity of milk by half or more. Put it in a pan on the stove, bring it to a simmer, and let it reduce. A wide-mouth pan such as a saucier will allow more surface area for faster evaporation. Keep the milk below the boil, to keep it from curdling, and make sure it doesn't scorch on the bottom of the pan, or you'll have a tough time scrubbing it off.