If you don't want to use canned green beans, you can cook frozen or fresh. For fresh you will definitely need a longer time to cook them. For frozen around 20 minutes of cooking at high temperature. Green beans need to be tender. So, pour water above the green beans, cover and crank the heat. Every 5-7 minutes, check to see if you need to add more water, and of course stir. Taste and see if they are tender or not. Green onions/scallions are optional, but they add a nice flavor to this green bean casserole. If you are using a microwave, I would add french fried onions after cheese is melted. You would need to cook it in the microwave for 6-7 minutes or until cheese is completely melted and cream of chicken soup starts to bubble up, then take the casserole carefully out and add onions. French fried onions are already crunchy, so to avoid getting them soggy, add them after. This could be also done the last minute before serving. NO SALT necessary. Cheese and Cream of Chicken soup have enough of sodium. If you do NOT eat chicken, you can use CREAM OF MUSHROOMS SOUP as a substitute. It's very good either way. Leftovers: Place chilled green bean casserole in an airtight container and keep it for up to 3 days. On that note... I don't like to keep my food longer than 3 days.