01Set the Instant Pot to sauté mode. Add the butter and melt. Add the onions, shallots, brown sugar, and salt. Stir to incorporate ingredients and coating the onions with butter. Cover with a saucepan pot lid and cook without stirring for 10 minutes.
02Remove the lid. Wearing an oven mit, hold the rim of the inner pot and stir onions. Continue to stir every 2 minutes, scraping the brown bits from the bottom. Continue to do this for 20 minutes, or until onions are caramelized and golden brown.
03Add the red wine. Use a wooden spoon to thoroughly scrape any brown bits stuck to the bottom of the Instant Pot.
04Stir in the broth, Worcestershire sauce, thyme, and bay leaves. Secure lid and seal valve. Cook on manual HIGH for 5 minutes.
05Allow natural pressure release for 15 minutes, then vent any remaining steam.
06Discard the bay leaves.
07Preheat the oven to broil. Line a baking sheet with parchment paper.
08Spread slices of bread with a thin layer of Dijon mustard. Top with Gruyere and parmesan cheese. Sprinkle with pepper.
09Place under the broiler for 3-5 minutes, until the cheese is bubbly and beginning to brown.
10To serve, pour soup into a bowl and top with a cheesy bread on top.