here 4 EGGS, 1 Spanish onion, 1 oz. of butter, 1 teaspoonful of vinegar, and 2 tablespoonfuls of breadcrumbs; pepper and salt to taste. Peel and slice the onion, and fry it brown in the butter; add the vinegar and seasoning when done. Spread the onion on a buttered dish, break the EGGS over them, dust these with pepper and salt, and sprinkle with breadcrumbs. Place a few bits of butter on the top, and bake until the EGGS are set, which will only take a few minutes.
http://vodworks.com/labs/ The Allinson Vegetarian Cookery Book, by Thomas R. Allinson (Year 1915)