Rich, hearty broth, crunchy bread and gooey cheese make this bowl of french onion and leek soup pure comfort food goodness.
Heat the butter over medium heat in a dutch oven or a large heavy-bottomed pot.
Add the onions and a dash of salt and cook over medium heat for 15 minutes. The onions should be very soft and pale golden.
Add the leeks, shallots, and garlic and continue to cook for an additional 15 minutes, stirring often. The mixture should be very soft and golden.
Reduce the heat to low, stir in the flour, and cook for 2 minutes. Add the light brown sugar, vinegar, and a pinch of salt and cook until onions are a deeply golden and very soft, an additional 15 mins.
Add the wine, bring to a boil, and then reduce to a simmer. Be sure to scrape up all the brown bits from the bottom of the pot as you deglaze with the wine.
Pour in the stock and stir in the thyme, bay leaf, salt and pepper (to taste). Cover and simmer for 30 mins.
Add the port and simmer uncovered an additional 5 mins.
Slice the baguette into rounds and lightly toast in the oven or a toaster.
Ladle the soup into oven safe bowls or crocks, top with a couple of rounds of toasted baguette and slices or a good sprinkling of the grated gruyere.
Turn your broiler up to high and broil the tops until melted and golden brown. Serve immediately.