Step 1

Put the olive oil in a large frying pan over a medium heat and fry the shallots until golden and caramelised, about 10 mins.

Step 2

Add the port, wine and herbs and simmer for 10 mins, or until reduced by half.

Step 3

Pour in the stock and continue to cook until reduced by half again, then strain, discarding the shallots and herbs.

Step 4

Transfer the sauce into a new pan and bring to the boil. Remove from the heat and whisk in the butter, then season to taste.