Saute onion and garlic with salt and sunflower oil for 5 minutes in a deep bottom pan. Keep the heat medium-high
This time, add your peppercorns to the sauteed onion
Add brandy and cook everything for 3 minutes
Add the beef stock and keep the heat high this time Keep stirring and cook for 10 minutes
Now you’ve to refrigerate the thick sauce in the fridge for 3 days
After the 3 days of refrigeration, take a pan and put on your stove. Now put the sauce into the pan and add whipping cream to it. Mix the whipping cream well and then add your 2 tsp of Dijon mustard
Now let the mixture simmer for 20 minutes with medium-high heat. But, keep stirring constantly
Your sauce is ready to serve