While the steak is cooking the sauce can be made and finished – simple.
4 sirloin steaks, weighing 200-250g
Salt and coarsely ground black pepper
Vegetable or corn oil for brushing
For the sauce
6 small shallots, peeled, finely chopped
A good knob of butter
1tbsp Dijon mustard
4tbsp crème fraîche
Preheat a ribbed griddle until almost smoking, season your steaks, lightly oil the griddle and cook the steaks for 3-4 minutes on each side for medium rare if they are thick.
While they're cooking, melt the butter in a saucepan and cook the shallots on a low heat for 1-2 minutes, stirring often, until soft.
Add the mustard and cognac and the stock and simmer until you have a couple of tablespoons left, then add the crème fraîche and simmer gently until the sauce thickens.
Season and serve with the steak.