Read the following text to answer questions 16 to 18

Creole Onion Soup

This is a traditional French dish adapted by the Creoles of New Orleans. It is sometimes known as 'Looney soup'.

Ingredients:

• 75 gr unsalted butter
• 6 large onions, peeled and sliced - Salt and pepper
• 1 tbsp brown sugar
• 600 ml beef stock
• 60 gr plain flour
• 2 tsp soy sauce
• 1 tsp Worcester sauce
• 6 slices of French bread
• 6 tbsp grated cheese

Method:

1. Melt butter slowly.
2. Add sliced onion, a pinch of salt and pepper and the sugar.
3. Cook on a low heat, stirring from time to time, until the onions have browned.
4. Add beef stock and bring to the boil.
5. Sift the flour, stirring hard to avoid lumps.
6. Add chicken stock.
7. Simmer for 3-4 hours.
8. Add sauces.
9. Top each bowl with bread and cheese and place under grill for two minutes, until cheese has melted. The bowls will be hot, so warn your guests. It is a very filling soup so you won't want much else to eat. It should be served for 4 to 6 people.

18. Simmer for 3-4 hours. " What does 'simmer' mean?