Preheat oven to 300 degrees F.

Season beef with salt and pepper. Heat 2 teaspoons oil in a Dutch oven or soup pot over medium-high heat. Add beef and cook, turning from time to time, until well browned on all sides, 5 to 7 minutes. Transfer to a plate.

Add the remaining 2 teaspoons oil to the pot. Add onions, reduce heat to medium and cook, stirring often, until softened and golden, 5 to 7 minutes. Add garlic and thyme; cook, stirring, for 1 minute. Stir in coffee and vinegar; bring to a simmer. Return the beef to the pot and spoon some onions over it. Cover and transfer to the oven.

Braise the beef in the oven until fork-tender but not falling apart, 2 1/2 to 3 hours. Transfer beef to a cutting board, tent with foil and let rest for about 10 minutes.

Meanwhile, skim fat from the braising liquid; bring to a boil over medium-high heat. Add the cornstarch mixture and cook, whisking, until the gravy thickens slightly, about 1 minute. Season with pepper. Carve the beef and serve with gravy. Slow-Cooker Variation: In Step 2, transfer the browned beef to a slow cooker. In Step 3, use just 1/2 cup coffee. Add the onion mixture to the slow cooker. In Step 4, cover and cook until beef is tender, 4 1/2 to 5 hours on High or 7 to 8 hours on Low. In Step 5, pour the liquid into a medium saucepan and continue as directed.

Ingredient Note: Although it is not the leanest cut of beef, chuck is still our choice for pot roast because it doesn't dry out during braising. You will find pockets of fat as you carve it, but they are easy to remove.

MAKE AHEAD TIP: Cover and refrigerate for up to 2 days.