In a large skillet melt the butter season the osso buco and sear them until golden brown on both sides.
When the osso buco is properly seared set aside in a bowl.
I the same skillet add the carrots, celery and onions and cook until translucent, add the tomato puree cook for an additional 3 minutes and deglaze with white wine.
When the wine is evaporated add the stock and let it reduce. Finish in the oven and cook for about 50 minutes. When the osso buco is ready, remove the meat from the juices, skim the excess fat from the sauce and let it reduce until correct consistency.
For the gremolata combine all the ingredients and set aside to finish the dish.
Serve the warm osso buco on top of a creamy saffron risotto and sauce with reduce liquid.