Preheat oven to 300.
Heat the Dutch oven over medium-high heat with a drizzle of olive oil. Liberally season the beef with salt and pepper, then dust with a thin coat of flour. Once heated, sear the chunks of meat in batches in the Dutch oven until they develop a browned crust, about 5 minutes per side. Once browned, set aside on a plate.
While the beef browns, prep your veggies. Peel and cut the carrots into 1 inch chunks. Peel and clean the leeks and cut the white and light green parts into 1/2 inch chunks. Peel and dice the onion into small pieces. Dice the tomatoes.
Once all the meat has been browned, remove it from the Dutch oven and set aside on a plate. Reduce the heat to medium and add the chopped onions to the pot. Sauté until beginning to brown, 2 minutes. Then add diced tomato and tomato paste, stirring until thickened, 2 minutes.
Add the wine and the beef stock to the pot and scrape up any browned bits stuck to the bottom. Add back in the beef with all its juices, the carrots, leeks and bay leaves. Place the lid on and carefully move to the oven.
Bake the stew until the beef is tender and easily shreds apart, about 4 hours. Check the stew at each hour mark, adding more beef stock if the liquid is reducing too much. Allow to cool completely, then serve on top of mashed potatoes or rice.