Preheat oven to 400° F. In a baking pan, brown the lamb bones in the oven.
In a large saucepan, melt the butter and sauté the shallots on medium heat for 3 to 5 minutes or until tender. Add the flour and cook, stirring constantly, for 5 minutes.
Add the thyme sprigs, wine, and stock and reduce by half. Add the browned lamb bones and simmer for 15 minutes. Strain the mixture and set aside. Keep warm.