French Onion Soup - Pankobunny

Ingredients

• 1 tbsp olive oil
• 4 tbsp salted butter
• 3 onions (sliced)
• 4 pieces of star anise
• 2 tbsp red wine vinegar
• 1 cup red wine (medium-full bodied)
• 900 ml beef stock
• salt and pepper (to taste)
• baguette (sliced into 4 one inch-thick slices)
• 300 g gruyere cheese (grated)