Season shanks on both sides with salt and pepper, to taste. Heat oil in a large rondeau until almost smoking. Add shanks and sear on both sides until golden brown. Remove shanks to a plate.
Add onion, carrots, celery, and thyme to the pan, season with salt and pepper and cook until the vegetables are golden brown. Return the lamb to the pan, add the wine, and cook until completely reduced. Add stock to cover and bring to a boil. Cover and place in the oven. Cook for approximately 2 1/2 hours or until the meat is very tender.
Strain sauce through a fine strainer into a medium saucepan. Add the serrano, sugar, and vinegar and cook until reduced by 1/2. Season with salt and pepper, to taste.
Serve with Sweet Potato Risotto with Roasted Chanterelles.
Sweet Potato Risotto with Roasted Chanterelles:
Place water in a medium saucepan and bring to a boil. Heat oil and butter in a medium high-sided saute pan. Add onion, season with salt and pepper, and cook until soft. Add rice and toss to coat in the mixture. Add wine and cook until completely reduced. Add 2 cups of the boiling water and cook until absorbed. Continue adding 1 cup of water at a time and cook, stirring often, until all liquid is absorbed. Repeat until rice is al dente.
Stir in the sweet potato and mix until combined. Add the butter and Parmesan, and season with salt and pepper, to taste. Fold in the pine nuts and reserved chanterelles, and scrape the mixture into a bowl. Drizzle with the balsamic glaze and the white truffle oil.
Preheat oven to 425 degrees F.
Place mushrooms in a medium baking pan, toss with oil and season with salt and pepper, to taste. Roast until golden brown, about 15 to 20 minutes.