Caramelize the onions

• Melt the butter in a stockpot over medium-low heat.
• Add the onions and cook slowly, stirring often, until deeply golden and soft.
• Add the garlic and thyme and cook until fragrant.

Add potatoes and deglaze

• Stir in the potatoes and cook briefly.
• Pour in the stout and scrape up the browned bits.
• Let the beer reduce slightly.

Simmer the soup

• Pour in the vegetable stock and season with salt and pepper.
• Bring to a boil, then lower the heat and simmer until the potatoes are tender.

Toast the bread

• Slice the baguette and toast the slices until crisp.

Gratinate and serve

• Ladle the soup into ovenproof bowls.
• Top with toasted baguette slices and grated cheddar.
• Bake or grill until the cheese is melted and bubbling.