01 - 
                Place quartered onion, smashed garlic cloves, and whole spices into the Instant Pot to create the aromatic base.
              
              
              
                02 - 
                Place the corned beef brisket into the pot fat cap side up, then pour beef broth over to cover the ingredients.
              
              
              
                03 - 
                Secure the lid tightly, ensuring the valve is set to 'seal'. Select the 'stew/meat' pressure cook setting and set the time to 75 minutes.
              
              
              
                04 - 
                After cooking completes, allow the pressure to release naturally for 20 minutes before performing a quick release to vent remaining pressure carefully.
              
              
              
                05 - 
                Transfer brisket to a baking sheet lined with aluminum foil, fat cap upwards. Spread spicy mustard evenly on top. Broil on low 8-10 inches from heat source until mustard caramelizes and browns, about 2-3 minutes. Monitor closely to prevent burning.
              
              
              
                06 - 
                Let the meat rest briefly. Slice brisket thinly against the grain for maximum tenderness. Serve with preferred sides or use in sandwiches.