Instant Pot Brisket

Name: Instant Pot Brisket
Ingredients: 1 tablespoon vegetable oil; 3 1/2 to 4 pounds beef brisket, fat cap trimmed to 1/4-inch thickness, cut into 3 or 4 pieces; Kosher salt and freshly ground black pepper; 2 yellow onions, thinly sliced (4 cups); ¾ cup ketchup; ¼ cup distilled white vinegar; ¼ cup packed dark brown sugar; 1 ½ pounds carrots, peeled and cut into 2-inch lengths (halved lengthwise if thick); 1 ½ pounds Yukon Gold potatoes, peeled and cut into 1 ½-inch pieces; Chopped parsley leaves, for serving