Onion Soup with Gruyere, Crostini and Balsamic Vinegar - De Nigris 1889

Ingredients

• 1/2 baguette, cut into slices
• 1 tbs. extra virgin olive oil
• 1 kg brown or white onions
• 120g butter
• 2 tbs. extra virgin olive oil
• 200ml dry white wine
• 1 tsp. caster sugar
• 1 tbs. sea salt flakes (or large pinch table salt)
• 2L vegetable or chicken stock – warm
• 250g grated Gruyere cheese
• 2 tbs. De Nigris Platinum Label Balsamic Vinegar