Heat the oil in a large oven-safe pot or Dutch oven and gently fry the beef for 2 to 3 minutes, until browned all over. Work in batches, if necessary. Remove from the pan and set aside.
Preheat the oven to 400 degrees
Add the onions and pancetta to the pot and cook for 5 minutes, stirring occasionally. Add the mushrooms, garlic, and carrot and continue to cook for another 5 minutes. Pour in the wine and bring to a boil.
Return the beef to the pot, stir in the tomato paste, and gently mix together well. Pour in the stock a little at a time, stirring as you do so, to create a sauce. Bring to a boil.
Toss in the rosemary and the bay leaf on top of the stew, cover the pot, and transfer to the middle of the oven to let bake for 25 minutes. Remove the lid for the last 5 minutes to allow the sauce to thicken slightly.
Before serving, season with salt and pepper and allow the stew to rest out of the oven for 10 minutes.