Place a rough cut of chuck roast or brisket into your slow cooker. Add diced onions, minced garlic, and beef stock. Set to low and cook for 6-8 hours until the beef is fork-tender.

Peel and quarter floury potatoes. Boil in salted water for 15-20 minutes until fork-tender. Drain and mash with warm milk or cream until smooth and creamy.

In a saucepan, melt butter over medium heat, whisk in flour to create a roux. Gradually whisk in reserved beef stock and cook until thickened, about 5-7 minutes.

Assemble by placing a slice of robust white bread on each plate, followed by tender beef, creamy mashed potatoes, and drizzle with homemade gravy.