Instant Pot Corned Beef

Name: Instant Pot Corned Beef
Ingredients: 1 large yellow onion, peeled and cut into 1/4-inch slices; 6 large cloves garlic, chopped; 4 sprigs fresh thyme; 2 bay leaves; 1 (3- to 4-lb.) package corned beef brisket, with seasoning packet; 12 oz. lager-style beer; 1 1/2 tsp. kosher salt, plus more to taste; 1 lb. small red potatoes, cut in half; 5 large carrots, peeled and cut into 2-inch pieces; 1 small head green cabbage, cored and cut into 8 wedges; Ground black pepper, to taste; Mustard, for serving