Crush peppercorns using a pestle and mortar or place in a plastic bag and crush using a rolling pin. Set aside.
Over low heat, melt the butter in a large skillet. Add the onion and garlic, sauteing until soft and fragrant.
Whisk in the flour to form a paste. Whisk in the cream until the mixture is smooth and bubbling.
Whisk in the beef broth, Worcestershire sauce, salt, sugar and crushed peppercorns.
Bring to a simmer, still over low heat, stirring occasionally. Simmer for 8-10 minutes, or until the mixture starts to thicken and coat the back of a spoon.
Remove from heat and serve.
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