Heat butter and oil in a saucepan over medium heat.
Add leeks and garlic. Cook, stirring often for 2 minutes
Add mushroom and bay leaf.
Mix in flour and cook for another 2-3 minutes.
Once mushroom softens, add chicken broth and season with salt if required.
After soup reaches a strong boil, remove bay leaf and blend half of the soup till smooth. You can skip this step if you prefer your soup to be all chunky.
Return soup to saucepan over medium-low heat.
Stir in milk, cream, black pepper and herbs.
Cook for a further 4-5 minutes, till the soup reaches a soft simmer but not boiling.
Add some broth/hot water if soup is too thick
Ladle into serving bowls, garnish and serve with garlic bread.