01 -
Cube the chuck steak into 1-inch pieces. Season generously with salt and pepper.
02 -
In a large heavy-bottomed pot, heat olive oil over medium-high heat. Add sliced onions, butter, a pinch of salt, and brown sugar. Stir frequently and cook over medium-low heat for 20 to 25 minutes until soft and caramelized.
03 -
Using tongs, remove caramelized onions from the pot and set aside. In the same pot, add additional olive oil if needed and sear beef cubes in batches over medium-high heat until browned on all sides. Remove beef and reserve.
04 -
Add minced garlic and thyme to the pot. Sauté for 1 minute. Pour half of the grape juice to deglaze, scraping any browned bits from the bottom.
05 -
Return caramelized onions and seared beef to the pot. Add remaining grape juice, Worcestershire sauce, Dijon mustard, flour, beef broth, and bay leaves. Stir to dissolve flour thoroughly.
06 -
Bring the mixture to a gentle boil, then reduce heat to low. Simmer uncovered for 90 minutes, stirring occasionally, until the beef is fork-tender and flavors are developed.
07 -
Preheat broiler on high. Arrange baguette slices on a baking sheet, brush both sides lightly with olive oil. Broil for 1 to 2 minutes per side until golden and crisp.
08 -
Ladle hot stew into bowls. Place toasted baguette slices on top, sprinkle generously with grated Gruyere cheese. Broil until cheese is melted and bubbly, then serve immediately.