In a bowl, mix together 1 large onion, thinly sliced, 4 cloves garlic, minced, 1 ounce packet beefy onion soup mix, 1 teaspoon dried thyme and 1/2 teaspoon dried rosemary until combined.
Spray the body of an 8-quart slow cooker with cooking spray. Add HALF of the onion mixture to the body of the cooker. Add ONE of the 2 (10.5 ounce) cans condensed French onion soup on top.
Pat the 2-3 pound chuck roast with paper towels. Season all over with 1 teaspoon kosher salt and 1 teaspoon black pepper.
In a large skillet over medium-high heat, add 2 Tablespoons vegetable oil. Once really hot, sear the roast on both sides to golden brown, about 5 minutes total (you are not fully cooking the roast, just giving it a good browning on both sides.)
Place the roast into the slow cooker. Top with the remaining onions. Pour the remaining can of condensed French onion soup on top.
Add the 1/2 cup unsalted butter, thinly sliced on top of the roast. Cover and cook on low for 6-8 hours or on high 4-6 hours until tender (DO NOT open the lid while cooking.)
Take the roast out of the cooker and set aside on a large plate. Shred the meat. Next, pour the liquid from the slow cooker into a a skillet or pot over medium heat.
In a bowl, mix 1/4 cup water with 2 Tablespoons cornstarch. Once the gravy is simmering, slowly stream in the cornstarch slurry while stirring constantly. Continue to simmer until the gravy has thickened.
Place the shredded roast back into the slow cooker and top it with the gravy, place on the warm setting until ready to serve.
When ready, serve with chopped parsley, for garnish (optional.)
Video
Notes
Browning (searing) is optional but I think it gives it great flavor.
You can use regular onion soup mix if you can't find beefy onion soup..
The onions add deep savory element to the dish but they are definitely not overwhelming so don't be afraid to use them.
There's tons of ways to reheat leftovers! Try using the slow cooker, stovetop, or microwave.
I enjoy serving this pot roast over mashed potatoes, but it is also good over egg noodles or rice. Feel free to try and see what your favorite way is.
You can skip the step of thickening the gravy, it is still very good as-is but just on the thin side.
The butter adds a richness to the dish but if you want to omit it, you can. No need to add anything in its place.
Storing any leftovers properly helps keep them flavorful. They should be stored in the fridge for up to 3 days, or freeze for up to 3 months.