Turn the Instant Pot on Sauté(more) mode and heat butter and oil.
Add onions, ½ teaspoon salt, ¼ teaspoon sugar and cook for 20-25 minutes stirring every 5 mins until onions turn golden brown but not burnt. Glass lid can be used during Saute process. After 20 minutes the onions should be golden brown and the bottom of the pot will start to brown.
Press Cancel. Add wine and deglaze the pot removing all browning from the pot. Cook for 2-3 minutes as the wine evaporates.
Add bay leaf, ½ tablespoon thyme, remaining salt, pepper, Worcestershire sauce, and 2½ cups of broth. Secure the lid with Pressure Release to Sealing. Pressure Cook (Hi) for 6 minutes followed by Quick Release.
Open the Instant Pot, remove the bay leaf and discard. Mix all purpose flour in the remaining broth and slowly stir in the soup. Set Instant Pot to Sauté mode and cook for 5 minutes as the soup thickens.
Preheat oven to broil(Hi). Cut each baguette slices into bite sized pieces. Line them on a baking sheet and toast until golden brown (5 to 7 minutes).
Add ¾ cup of soup to an oven safe bowl. Add toasted bread pieces and top them with handful go shredded Gruyere cheese, top with Swiss cheese slices and a sprinkle of cayenne pepper and thyme. Broil for 5 mins or until the cheese melts. Serve hot!
Use a mix of red and yellow onions.Dry thyme can be substituted for fresh.