Autumn Soup au Gratin with Onion and Apple

Ingredients

• 2 tbsp (30 mL) butter
• 4 cups (1 L) onions, thinly sliced
• 2/3 cup (160 mL) apple cider or unsweetened apple juice
• 2-1/2 cups (675 mL) veal stock or beef broth
• 1/2 tbsp (7 mL) Dijon mustard
• 3/4 cup (180 mL) apples, peeled and diced
• Salt and ground pepper, to taste
• 8 slices baguette bread, toasted
• 2 cups (500 mL) Canadian Gouda, grated