Season and sear the beef

• Pat the beef chuck roast dry and season generously all over with salt and black pepper.
• Heat the olive oil in a frying pan over high heat and sear the roast on all sides until deeply browned.

Sauté the aromatics

• Lower the heat and add the onion, carrots and smashed garlic to the pan.
• Cook until the onion softens and picks up color, scraping up the browned bits.

Build the braising liquid

• Stir in the tomato paste and cook briefly, then pour in the apple cider and beef broth.
• Add the Worcestershire sauce, Dijon mustard, thyme sprigs and bay leaves, and stir to combine.

Slow cook the pot roast

• Transfer the seared roast and the liquid with vegetables to the slow cooker.
• Cover and cook on low until the beef is fork tender.

Roast the garlic

• Drizzle the halved head of garlic with a little oil, wrap in foil and roast until the cloves are soft and golden.
• Squeeze the roasted cloves out of their skins and mash into a paste.

Boil the potatoes

• Place the potatoes in a stockpot, cover with cold salted water and bring to a boil.
• Cook until a knife slides in easily, then drain well.

Make the roasted garlic mashed potatoes

• Mash the drained potatoes with the butter, warmed heavy cream and sour cream until smooth.
• Fold in the roasted garlic paste and grated Parmesan, then season with salt and pepper to taste.

Thicken the sauce

• Strain the cooking liquid from the slow cooker into a saucepan and bring to a simmer.
• Whisk in the cornstarch slurry and simmer until the gravy thickens.

Serve

• Shred or slice the pot roast and spoon the gravy over it.
• Serve alongside the creamy roasted garlic mashed potatoes.