Heat the oil in a shallow pan (that you have used to cook your steak) over a medium heat. Add the shallots and garlic with a pinch of salt stirring frequently. Cook for 5 minutes.
Pour in your brandy and flambé. Add the wine and flambé again. Reduce the volume of liquid by two-thirds.
Once the wine has reduced, and the stock and simmer.
The finished sauce should coat the back of a spoon, so if it hasn’t reached the right consistency just keep reducing the sauce in the pan before adding the chopped bone marrow.
Warm through and add the fresh herbs, a squeeze of lemon juice, check for seasoning and serve with a steak.
