Ingredients
For the steaks:
500g ground Wagyu beef 
Salt and pepper to taste 
For the sake onion confit:
2 large onions, sliced 
1 tbsp butter 
2 tbsp brown sugar 
50ml sake (or a non-alcoholic substitute like sweet stock) 
For assembly:
4 brioche burger buns 
200g brie, sliced 
4 lettuce leaves 
1 tomato, sliced 
Mayonnaise or sauce of your choice (optional)
Instructions
Prepare the sake onion confit:Melt butter in a skillet over medium heat.
Add sliced onions and cook until soft and translucent (about 10 minutes).
Stir in brown sugar and stir. Let caramelize slightly.
Deglaze with sake and balsamic vinegar. Let simmer until liquid reduces and thickens. Set aside.
Form Wagyu steaks:Divide Wagyu beef into 4 portions and form into steaks.
Season generously with salt and pepper.
Cook steaks:Heat a skillet or grill over medium-high heat.
Cook steaks for about 3-4 minutes per side (or to your preferred doneness). Let rest for a few minutes. 
Add the melted brie:Place a slice of brie on each hot steak. Cover with a lid or aluminum foil to melt it slightly.
Prepare the buns:Lightly grill the burger buns until they are golden and crispy.
Assemble the burgers:Spread the base of the bun with a little mayonnaise or sauce if desired.
Add a lettuce leaf, a slice of tomato, then the Wagyu steak with brie.
Garnish generously with the sake onion confit.
Close with the bun cap. 
Serve immediately: Accompany with homemade fries or a green salad. 
Time :
Prep : 20 min
Cook : 20 min
Total : 40 min
Kcal :
Approx. 650 kcal per portion | 4 burgers