Heat the oven to 150°C fan.
Cook bacon lardons in olive oil in a heavy cast-iron pot over medium heat, 5 to 6 minutes, until golden. Lift out.
Brown the beef in three batches in the bacon fat, 6 to 8 minutes per batch, getting a proper dark crust. Remove to a plate.
Add butter. Soften the onion and carrots over medium heat for 8 minutes. Add garlic, stir 30 seconds.
Sprinkle over flour, stir for 1 minute. Stir in tomato paste, cook another minute.
Pour in wine. Bring to a simmer, scraping the fond. Simmer 5 minutes.
Return beef and bacon with their juices. Add stock, brown sugar, bouquet garni. Season.
Lid on, oven 3 hours. Check at 90 minutes, stir, top with a splash of stock if dry.
In a separate pan, saute pearl onions in butter for 10 minutes until golden. Remove. Saute mushrooms hard for 5 minutes until browned.
After 3 hours, stir onions and mushrooms through. Return to oven 15 minutes.
Taste, adjust seasoning. Serve over buttered pappardelle or mash. Scatter parsley.