Bakso Bawang Perancis Panggang

Bahan-bahan (8 porsi)

• 1 1/4 pounds ground chicken
• 1 slice soft whole grain bread
• 1 egg, beaten
• kosher salt and black pepper
• 6 tablespoons salted butter
• 3 -4 medium yellow onions, thinly sliced
• 3/4 cup dry white wine, such as Pinot Grigio or Sauvignon Blanc
• 3 cloves garlic, chopped
• 2 cups cremini or wild mushrooms, sliced
• 2 tablespoons fresh thyme leaves
• 2 tablespoons chopped fresh sage
• 2 1/2 cups low sodium chicken or vegetable broth
• 1/4 cup whole milk, cream, or canned coconut milk
• 6 slices french bread
• 1 cup shredded gruyere cheese