Melt butter in a heavy based casserole pot over medium heat. When it starts to foam, add onions and stir to coat in butter.

30 min on medium low: Turn heat down to medium low. Cook for 30 minutes stirring every few minutes, until the onions have softened and are semi transparent.

Salt, 20 min on medium high: Turn heat up to medium or medium high. Add salt, and cook for a further 20 - 30 minutes, stirring more regularly, until onions are deep golden and sweet.

Deglaze: Add wine, then simmer rapidly for 2 minutes until mostly evaporated, stirring to scrape the bottom of the pot.

Flour: Sprinkle flour over the onion and cook for 1 minute.

Add broth & herbs: Add broth, thyme and bay leaves.

Simmer: Cover, lower heat so it's simmering gently then simmer for 30 minutes.

Serve: Season to taste with salt and pepper. Ladle into bowls. Top with 1 or 2 slices of cheesy toast.

Preheat grill / broiler to high.Toast each side of bread until light golden.

Top bread with cheese, then grill until melted and some brown spots appear.