French Onion Soup with Thyme and Gruyère Crostini

INGREDIENTS

• 1 pound yellow onions, halved and thinly cut lengthwise
• 3 to 5 sprigs of fresh thyme
• 1 bay leaf
• 1/4 teaspoon sea salt
• Fresh cracked pepper
• 1 teaspoon all-purpose flour
• 1/2 cup dry white wine
• 2 cups beef stock
• 1 cup water
• 1 1/2-inch-thick slice of ciabatta bread cut in half
• 2 tablespoons unsalted butter
• 1 1/2 cups grated Swiss Gruyère cheese