Ingredients: Clear soup, savoury custard.
Make a savoury custard and divide it into three parts, one to be left white, another coloured red with tomato, and the third green with spinach. Put a layer of each in a buttered saucepan and cook for about ten minutes, cut it into dice, so that you have the three Italian colours (red, white, and green) together, then put the custard into a soup tureen and pour a good clear soup over it.
See also: Wikipedia Cookbook.
Source: ''The Cook's Decameron: A Study In Taste, Containing Over Two Hundred Recipes For Italian Dishes'' from a project that puts out-of-copyright texts into the public domain. This is from a *very* old source, and reflects the cooking at the turn of the last century. Update as necessary.