heat the ghee in a small frypan and fry onion and garlic
remove 2 teaspoons of onion/garlic mix and set aside
Add several grinds of black peppercorns
when coloured add whiskey and reduce to almost nothing
add stock, reduce
whisk in butter and lemon juice
Sauce is perfect as is now, but if you have mushrooms why not use them?
set aside in seperate pan and wipe pan clean (you will find your finger is perfect for this task and will involve many "mmmmmm..." noises.)
Melt ghee and butter in pan, fry mushrooms.
Add reserved onion/garlic mixture
remove a few mushrooms and set aside for garnish
Add sauce back to pan, stir.
Serve sauce with reserved mushrooms as garnish