Cut onions into large chunks and place into pressure cooker with bay leaves. Pour chicken broth or water on top.
Put a trivet into the middle of your pot with frozen pork roast on top. Sprinkle with salt and pepper.
Close lid and steam valve, push meat/stew button and set for 55 minutes.
Allow pressure to release naturally when done.
Remove meat and cover to keep warm. Discard bay leaves. To make gravy set pot to saute, remove trivet.
In a small bowl whisk together 1/4 c of the hot liquid (minus onions) with 2 tbsp cornstarch until slurry is smooth.
Pour this in once mixture is bubbling. Stir to thicken. Make creamy with 2 tbsp of half and half into the mixture too. Turn pot off and pour gravy into dish so it doesn't continue cooking.