- Peel onions. Then cut each in half lengthwise, slicing through the root end. Place onions cut-side down on a chopping board, then thinly slice into half-moon pieces. Sliced onions should measure about 5 cups (1.25 L).
- Heat butter and oil in a large wide saucepan over medium heat. Add onions, then sprinkle with sugar. Cook, uncovered and stirring often, until very soft and caramelized, about 15 min. Reduce heat if they brown too quickly.
- Add broth, wine, Dijon and seasonings. Scrape up brown bits from pan. If using a carton of broth, add 1/2 cup (125 mL) water. For canned, add 3 cups (750 mL) water. Bring to a boil over high. Then cover and simmer over medium-low for 30 min to develop flavour. Discard bay leaf and thyme sprigs.
- Place oven rack in top half of oven. Preheat broiler. Cut bread into 8 slices, each 1/2 in. (1 cm) thick. Butter both sides of each. Toast on a baking sheet until lightly golden, about 2 min per side.
- Place oven-safe soup bowls on a baking sheet. Ladle in soup. Top each with 2 toasts. Sprinkle with cheese. Place sheet in oven. Broil until cheese is bubbly, 2 to 4 min. Serve immediately. If making ahead, soup (without toasts) will keep well in the fridge for 3 days or freeze for up to 2 months, and flavour will improve as it sits.
Switch it up
BROTH: For a milder flavour, replace beef broth with chicken. (If using chicken broth from a carton, omit water.) Or boost taste by adding 2 tbsp (30 mL) brandy or a 14-g pkg of dried mushrooms.
CHEESE: Try a stronger, nippier cheese, like grated asiago, or a crumbled blue cheese such as gorgonzola or stilton.
SERVING: No heatproof dishes? Use an oven-safe saucepan. Create a raft of cheese-topped toasts on soup in the pan. Place in oven and broil until toasts are golden, 5 to 10 min.