Set the pressure cooker to "sear", press "start/stop", and add the bacon. Cook until crisp. Remove bacon and drain on paper towel; set aside.
Add butter to pressure cooker to melt. When melted, add onions and cook until tender. Pour in 1 qt chicken stock. Add sea salt, ground pepper, and parsley.
Place the rack in bottom of cooker and place the potatoes on the rack.
Close and lock lid. Set to "soup", adjust time to 4 minutes, and press "start/stop".
When done, quick release and make sure all pressure is released before opening the lid.
Carefully open. Using tongs, carefully remove potatoes and transfer to a plate or bowl, set aside. Using oven mitts, remove rack from pressure cooker.
In a small mixing bowl, add cornstarch and water. Mix well to dissolve the cornstarch.
Set pressure cooker to "sear", press "start/stop", and add cornstarch mixture. Stir well.
Add shredded cheese and cream cheese to soup. Stir until cheese is melted.
Pour in remaining chicken stock and half & half. Add corn, reserved bacon, and return potatoes to cooker.
Check seasoning and add salt and pepper, if needed. Ladle into serving bowls. Serve with shredded cheddar cheese and scallions
as garnish.