Melt the butter in a large pan, add the flour and quickly use a whisk to make a roux. Continue whisking and add 1/2 gallon of milk. Keep stirring until the mixture is cooked and smooth. Rinse the beef, chop it into pieces and add to the white sauce above. Add salt, pepper, and sugar to taste. Serve hot over bread, biscuits, or toast. We like to add frozen peas (cooked) when ready to serve.