Brown the beef

• Season the chuck steak liberally with salt and pepper.
• Heat the butter and olive oil in a searing hot Dutch oven and brown the beef in batches.
• Remove the browned beef and set aside.

Braise the beef

• Add the roughly chopped carrots, celery and red onion to the same pot and cook for 3 to 4 minutes.
• Return the beef, then add the red wine, beef broth, halved garlic heads and tied herbs.
• Cover and cook at 165 °C until the meat falls apart.

Cook and mash the potatoes

• Boil the potatoes in heavily salted water until tender, then drain.
• Let them steam dry under tea towels for 5 minutes.
• Pass them through a ricer or mash, then fold in the milk, butter and half of the Gruyère.

Cook the vegetables

• Heat the olive oil in a large skillet and cook the diced onion, carrots and celery until soft.
• Add the minced garlic and tomato paste and stir to combine.
• Turn off the heat.

Shred the beef

• Once cooled, shred the beef by hand.
• Add it to the skillet and turn the heat back on low.

Thicken the filling

• Strain the braising liquid into the pan and bring to a low simmer.
• Make a slurry with the melted butter and flour, then stir it in.
• Season to taste and let it thicken.

Assemble the pie

• Spoon or pipe the mashed potatoes over the beef.
• Sprinkle the remaining Gruyère and the Parmesan over the top.

Bake and rest

• Bake at 200 °C for about 30 minutes.
• Broil for a few minutes to brown the top, keeping a close eye on it.
• Rest for 10 to 15 minutes before serving and top with chives if you like.