Peppercorn Sauce - Cooking like a Boss

2tbsp 0.03l 30ml 6tsp 0.127cup 0.053pint butter		fry until soft	reduce by half	simmer 15mins
2 small onion	finely chopped
2 clove garlic	smash and finely chop
300ml 0.3l 20tbsp 60tsp 1.27cup 0.528pint dry white wine
300ml 0.3l 20tbsp 60tsp 1.27cup 0.528pint double cream
4tbsp 0.06l 60ml 12tsp 0.254cup 0.106pint whole peppercorns	cracked in pestle and morter
1tsp 0.005l 5ml 0.333tbsp 0.021cup 0.009pint salt
2tsp 0.01l 10ml ²⁄₃tbsp 0.042cup 0.018pint freshly ground pepper