Melt butter over medium heat in a medium frying pan. Add shallots and cook until fragrant and translucent, about 3 minutes.
Add in garlic and peppercorns and cook until fragrant and the edges of the garlic begin to lightly brown, about 1 - 2 minutes.
Add in Worcestershire and beef stock and stir to fully combine, making sure you scrape down the bottom of the pan to prevent sticking.
Pour in heavy cream and add salt to taste.
Bring mixture to a boil and then reduce the heat so the mixture is at a simmer.
Cook about 10 minutes, stirring frequently until the mixture thickens. It should coat the back of a spoon.
Remove from heat and set aside until ready to assemble.