For the port and redcurrant jus, melt a knob of butter in a large saucepan on a medium-to-high heat.
Add 4 shallots, peeled and sliced, 2 fresh thyme sprigs and 2 garlic cloves, peeled and chopped and fry for a few minutes to just brown the edges.
Add the fennel seeds and toast for 1 minute then stir in 50g dark brown sugar until it melts through and begins to bubble up the side of the pan.
Reduce the heat, stir in 150ml red wine to deglaze the pan for a minute or so and then add 250ml of beef stock, 3 tablespoons of good-quality port, 30g tomato paste and 50g redcurrant jelly.
Bring to the boil and simmer for 15 minutes - this will evaporate off most of the alcohol, leaving a rich, sweet and syrup-like sauce.