(Optional) Use butcher's twine to tie up the tenderloins in a round shape, this will help them cook evenly

Crush 3/4 of the peppercorns with a meat hammer or a rolling pin

Press peppercorns on the tenderloins, both sides. Save some of them for later.

Melt butter on a frying pan and cook tenderloins as you like it. I like them medium, 4 minutes each side

Keep the tenderloins warm (on a hot plate or under an aluminum foil)

Pour brandy and mustard in the same frying pan you used before

Stir and cook on low heat for 1 minute

Add double cream and the green peppercorns you saved before

Cook on low heat until thicken

Put the tenderloins in the frying pan with the sauce you just made, few seconds are enough