Start by peeling and roughly chopping the onions and placing in a heatproof pan.
Add hot water and place under the meat to be roasted.
Once the meat is ready, remove the tray and empty contents in the saucepan.
Heat over medium to high heat, add stock and wine and bring to a simmer.
Once at a simmer, lower heat and reduce contents by about a third.
Melt butter in a separate pan and add flour, whisk constantly until a nice nutty color is achieved.
Add flour and butter to the gravy mixture to help thicken, taste and season with salt and pepper if needed.
Strain contents and serve.