In a large bowl, add the beef, flour, salt, and pepper. Mix until each piece is well coated. Set aside.

Warm 2 tablespoons canola oil in a large (6-quart) pot over medium-high heat for about 2 minutes.

Add the chopped onion and cook until translucent, about 3 minutes. Stir in the garlic and cook less than 1 minute, until fragrant.

Add the floured beef. Cook until browned on all sides, stirring occasionally — roughly 10 minutes. Don’t overcrowd; work in batches if needed.

Pour in 1 cup Irish stout and bring to a boil for 5 minutes, scraping browned bits off the bottom.

Stir in 3 tablespoons tomato paste and 1 teaspoon dried thyme, then pour in 32 ounces beef stock. Stir to combine.

Add the carrots and quartered potatoes. Bring the pot to a boil, then reduce heat and let simmer for 30 minutes, or until the potatoes and carrots are tender. Remove from heat.

Scoop 1/4 cup of the stew broth into a small bowl. Whisk in 2 tablespoons cornstarch until smooth to make a slurry. Stir the slurry back into the stew and return to a gentle simmer for 1–2 minutes until the broth thickens.

Taste and adjust seasoning with salt and pepper. Serve hot, topped with chopped parsley if desired.