Preheat the oven to 160°c. Cut your beef into 1-2 inch pieces.
In a large bowl, toss the beef with the flour and a large pinch of salt and pepper and set aside.
In a large cast-iron cocotte, render the fat from the lardons over medium-low heat until the edges of the bacon are crispy. Remove the bacon to a large bowl, leaving the rendered fat in the pan.
Increase the heat to medium high. Add the beef to the fat in the pan and brown it on all sides. Remove the beef from the pan to the bowl with the bacon.
Add diced onion, sliced rounds of carrot, and half the sliced mushrooms to the pan. Reduce the heat to medium and cook for 5 to 7 minutes or until softened. Add the garlic and cook for another 30 seconds or until aromatic.
Remove vegetables from the pan to a bowl. Deglaze the pan with the cognac and cook until reduced by half, scraping the bottom of the pan to release any browned bits.
Add the wine, stock, tomato paste, herbs, brown sugar, and a big pinch of salt and pepper. Bring to a boil, then remove from the heat.
Return the lardons, beef, and vegetables to the pot. Cover and place in the oven. Leave for 1 hour before removing to check and stir. Put back in oven for another hour.
In the meantime sauté the remaining mushrooms in a pan with butter and set aside.
If using pearl onions caramelise with sugar and butter and set aside. Taste for seasoning and adjust if necessary.
Once the two hours is up add the onions and mushrooms and cook for a further 30 minutes to 1 hour or until the beef is fork-tender.
Remove from the oven, taste, and adjust the seasoning with salt and pepper if needed.
Stir in some freshly cut flat leaf parsley and serve.