Broccoli and mushroom soup

Ingredients

For the stock:

• 1 tbsp salted butter
• 2 sticks of celery - cut into pieces
• 1/2 ( about 80g) carrot - cut into pieces
• 1 large onion - quartered
• 1/2 liter of water

Other ingredients:

• 300g broccoli - cut into florets
• 200g button mushrooms - sliced
• 5 garlic - chopped
• 5 shallots - chopped
• 2 spring onions - sliced
• 3 tbsp oil
• pepper and salt to taste