Heat 1 Tbsp olive oil in a large skillet or Dutch oven over medium-high heat.

Pat the chuck roast dry with paper towels and season it generously with salt and black pepper.

Sear the roast for 4–5 minutes on each side, until a deep golden crust forms. Transfer to the slow cooker.

Add the remaining ½ Tbsp of olive oil to the same pan.

Add sliced onions and sauté for 2 minutes, just until they begin to soften.

Stir in the minced garlic and cook for another 30 seconds until fragrant.

Transfer the onion mixture over the roast in the slow cooker.

Return the pan to heat and pour in the beef broth, Worcestershire sauce, thyme, and rosemary.

Stir and scrape up the browned bits from the bottom of the pan—this step adds tons of flavor.

Pour the broth mixture into the slow cooker over the onions and beef.

Layer the whole Yukon gold potatoes and chopped carrots over the roast.

Season everything with a little extra salt and pepper.

Cover with the lid.

Cook on low for 8–9 hours, or until the roast is tender and the vegetables are soft.

If using high, cook for about 5–6 hours.

Remove the roast and vegetables from the slow cooker.

Shred the roast with two forks, discarding any large pieces of fat.

If desired, cut the potatoes into halves or quarters for serving.

Strain the broth through a fine mesh sieve into a small saucepan.

Heat over medium-high. In a small bowl, whisk 2½ Tbsp cornstarch with 3 Tbsp beef broth.

Slowly whisk the slurry into the simmering broth and cook for 30–60 seconds, until thickened.

Plate the shredded beef and vegetables, drizzle with the gravy, and sprinkle with fresh parsley.