Heat a frying pan over medium heat and add the butter and shallots (ideally, use a pan that you just cooked steak in!)
Once the shallots are softened, add the brandy or cognac and let the mixture simmer for a few minutes.
Add the stock, cream, and Salted Peppercorns.
Simmer gently for 3-5 minutes, stirring frequently.
Meanwhile, make a slurry by mixing the cornstarch with a bit of water.
Thicken the sauce by pouring some of the slurry in and quickly incorporate it in with a spoon. Add more until the sauce has thickened to your preference, and serve immediately.
