Season chuck roast very generously with salt and pepper.
Heat a little oil over high heat in a Dutch oven.
Sear all sides of the chuck roast for five minutes each until it gets a nice crust.
Set roast aside and reduce heat to medium.
Melt butter in the same pan and add the onions.
Reduce heat to low or medium low and slowly cook onions until golden and translucent, about an hour.
Preheat oven to 325°F.
Add minced garlic and flour to the pan, turn heat to medium and let flour get golden.
Add cognac and white wine and let absorb.
Add beef broth slowly.
Add salt and pepper to taste.
Return roast to pan.
Cover and bake for 3 to 3 ½ hours or until fork tender.
Remove from oven and discard thyme and bay leaves.
Shred beef into large pieces.
Arrange toasted baguette slices on top and top with gruyere cheese.
Broil until cheese is golden.
Top with fresh thyme and serve.
