In a pot, cook the shallots and garlic in the olive oil until the shallots are soft and caramelised. Add the mushroom trimmings and sweat for 5 minutes. Add the port and red wine. Simmer the liquid until it is reduced by two-thirds. Add the beef stock and simmer for 45 minutes until the liquid has reduced to 1 litre.
Strain the liquid through a muslin cloth without forcing any liquid th