Mix the spice packet, black pepper, and garlic paste in a small bowl. Spread the garlic/spice blend evenly over the fat layer of the brisket.
Place the onions, thyme, bay leaves, and chicken broth in the pressure cooker. Then place the trivet on top.
Place the brisket on top of the trivet, lock the lid, and cook for 75 minutes at high pressure. When the cooking time is complete, allow the pressure to release naturally, which may take about 30 minutes.
Switch to an air fryer lid and broil the brisket at 400 F degrees for 10 minutes. Then remove the brisket from the pot, cover it with foil to keep it warm, and allow it to rest.
If you don't have an air fryer lid, transfer the brisket to a baking sheet. Turn the oven to its HIGH BROIL setting. Place brisket on the bottom rack of the oven and cook for 5-10 minutes, depending on how hot your broiler gets and how crispy you prefer your corned beef. Once the moisture cooks off, it will begin to toast very quickly, so keep a close eye on it. Once the brisket has reached your preferred char level, set it aside and allow it to rest for at least 10 minutes before slicing.
Always slice against the grain for maximum tenderness.
Pour liquid into a separate container using a fine mesh strainer, then return to the pot. Discard the aromatics. Add carrots and potatoes to the pot, then top with cabbage. Do not mix; you want the carrots and potatoes submerged, but the cabbage steams fine. Lock the lid and cook for 0 (zero) minutes at high pressure. If your cooker will not allow you to set it to 0, 1 minutes works just as well. Once cook time is complete, quick-release pressure and mix well. Note: You could opt to roast the vegetables in the oven while the brisket cooks in the pressure cooker.