Set the electric pressure cooker to sauté. Once hot, add the butter and allow it to melt.
Add the sliced yellow onion and baking soda. Toss until the onions are evenly coated in butter. Cook, stirring regularly, until the onions soften and develop a golden-yellow color.
Add the minced garlic and cook briefly until fragrant.
Pour in the water, scraping the bottom of the pressure cooker thoroughly to release any browned bits.
Stir in the halal Worcestershire sauce, balsamic vinegar, and beef bouillon base until the bouillon has completely dissolved. Turn off the sauté function.
Sprinkle the dry orzo evenly into the liquid. Add the cubed chicken, dried thyme, and black pepper on top. Avoid vigorous stirring at this point.
Secure the pressure cooker lid and set the valve to sealing. Pressure cook on high for 1 minute.
When the cooking cycle ends, allow the pressure to release naturally for 5 minutes. Carefully move the valve to venting to release the remaining pressure.
Remove the lid and stir the French Onion Chicken Orzo Casserole thoroughly. The orzo should be tender and creamy.
Stir in the heavy cream, mozzarella, and Parmesan until the cheeses melt and create a creamy sauce.
Spoon into serving bowls or plates and finish each portion with crispy French fried onions.