Start by trimming off the fat from the larger bones. Place oxtails in a roasting pan and salt & pepper the bones generously. Put pan in an oven, pre-heated to 450 degrees, for about 20 minutes or until the meat starts to brown. Transfer oxtails to a pot, add the thyme, bay leaves, garlic and cover with water. (You can add a cube or two of beef bouillon to kick-start the whole thing.) Bring to a boil and simmer for 2.5-3 hours, adding water to keep the meat covered. Remove the oxtails and let cool. Strain the broth, let cool and then refrigerate overnight leaving the fat layer. Remove the meat from the bones while they are still warm and refrigerate the meat.
After it cools for a few hours the broth will have a hardened fat cap, which can easily be removed. I use some of the fat to sauté the mushrooms and make the roux to thicken the broth in place of the olive oil and butter.
Next, sauté the mushrooms in a very hot pan to give them some color before they release their water. Set mushrooms aside. Melt the butter (or fat) in the same size pot as the stock was made and add the flour to the melted butter, whisking constantly to make a roux. Once the roux is roughly the color of peanut butter, add the onions and stir together until onions are translucent. Add the mushrooms, oxtail meat and stock to the pot and bring to a slow simmer for 10-15 minutes or until the broth has thickened. Salt and pepper to taste.
Add a pour of sherry to bring out more flavor. Don’t bother with ‘cooking sherry’, make it a decent sherry. As with wine, if you won’t drink it on its own, don’t add it to your food.
Serve over egg noodles, pasta, spätzle or any other starch you like.