Remove the onglet steaks from the fridge and pat dry with kitchen paper to allow them to come to room temperature while you make the sauce.
Peel and finely chop the garlic and shallot.
If you are using dried peppercorns, place them in a bowl with some boiling water to allow them to rehydrate.
Melt the butter in a frying pan over a medium heat and add the shallots, occasionally stirring for about 5 minutes until the shallots have softened but not coloured.
Add the garlic and green peppercorns and cook for a minute then add the brandy for a further minute.
Add the stock, bring to a simmer and allow the liquid to reduce by half then turn off the heat.
Use a pastry brush to oil the steaks and season with the salt and pepper just before cooking.
Heat the griddle over a high heat and add the steaks.
Turn the steaks after 2 minutes then cook for a further 2 minutes.
Reduce the heat to medium and add the butter, basting and turning every 30 seconds for about 2 minutes to 4 minutes.
Remove the onglet steak from the pan to a plate covered with foil to allow the meat to rest while the sauce is finished.
Reheat the sauce over a medium heat and add the cream until it simmers for a few minutes and thickens.
I like to add any juices from the beef resting plate at this point.
Check the seasoning.
If you prefer a thicker sauce, combine a teaspoon of cornflour with water and stir into the sauce.
Serve the steak sliced across the grain with the green peppercorn sauce.