Preheat grill on high.
Heat the butter in a large saucepan over medium heat.
Add the onions and garlic and cook while stirring for 15 minutes or until the onions are soft and slightly golden brown.
Add the flour and cook for 1 minute.
Add the wine and cook for another minute.
Stir in the stock, thyme and bay leaves and bring to the boil.
Reduce heat and simmer, uncovered, stirring occasionally, for 30 minutes or until soup thickens slightly.
Remove thyme and bay leaves. Season with salt and pepper to taste.
Place bread slices on a baking tray and grill for a minute on each side or until a lightgolden colour.
Remove from grill and sprinkle cheese evenly.
Return under the grill and cook for a further 2 minutes or until the cheese melts and is golden brown.
To serve, ladle soup into serving bowls and top with the chessy toasts.