Start by cubing the chuck steak into bite-sized pieces and slice the onions thinly. Mince the garlic.

In a large pot, heat the olive oil over medium-high heat. Season the cubed beef with salt and pepper, searing it for approximately 5-7 minutes until browned. Remove the beef and set aside.

Lower the heat and add butter to the pot. Once melted, add the sliced onions with a pinch of salt, stirring occasionally for 25-30 minutes until caramelized.

Stir in the brown sugar, thyme, minced garlic, Worcestershire sauce, Dijon mustard, tomato paste, and flour into the onions. Cook for 2-3 minutes.

Deglaze the pot with dry grape juice and return the seared beef. Add beef broth and bay leaves.

Bring to a boil, then simmer on low for about 90 minutes, stirring occasionally.

Preheat oven to 400°F (200°C). Slice baguette and brush with olive oil, adding a layer of Dijon mustard, Gruyere, and Parmesan cheese. Bake for 10 minutes.

Remove bay leaves from the stew and serve in bowls, topping with cheesy bread slices.