Preheat oven to broil.
Slice the onions in half and then slice the onions into small slices about a 1/4th of an inch thick. I like to use a mandolin slicer because it's fast and much easier.
Place the Instant Pot on Saute mode (if you have the "more" button on your IP use that). When hot, add the butter and olive oil.
When the butter and olive oil have melted, add the sliced onions to the pot. Stir.
Allow the onions to cook for about 10-25 minutes (stirring frequently so they don't scorch or burn) until the onions have become translucent and golden in color. The longer you cook them the more caramelized the onions. It's your decision.
Add the beef broth, wine, Better than Bouillon, brown sweetener, garlic, thyme, salt and pepper to taste, and the bay leaf to the pot. Stir.
Place the lid on the pot and seal. Cook for 8 minutes on Manual > High-Pressure Cooking.
When the pot indicates it has finished, quick release the steam.
Open the pot and spoon the soup into oven-safe bowls. Top with shredded cheese. Keep in mind, cheese melts down a lot. If you want a thick gooey layer of cheese on top, you will have to pile a nice amount of cheese over the soup.
Broil for 1-2 minutes or until the cheese melts.