Prepare the ingredients as instructed.

Place the sliced cucumber into a pitcher with the water and refrigerate to infuse while preparing the rest of the meal. Serve over ice when ready.

Heat the olive oil in a heavy-bottomed pot over medium heat. Add the sliced onions and cook, stirring often, until softened, about 10 minutes.

Increase the heat to medium-high, add the butter, and continue cooking the onions for about 20 minutes, stirring frequently, until they begin to brown.

Sprinkle the onions with sugar and salt and continue cooking for about 10 more minutes, stirring often, until deeply caramelized.

Add the garlic and cook for 1 minute until fragrant, being careful not to burn it.

Deglaze the pot with the Chardonnay wine, scraping up any browned bits from the bottom.

Add the beef broth, bay leaf, thyme, and black pepper. Bring to a gentle simmer, then cover, reduce heat to low, and simmer for about 10 minutes. Remove and discard the bay leaf, taste, and adjust seasoning as needed. Stir in the brandy if using.

Preheat the broiler to low. Lightly brush the sourdough slices with olive oil and place them on a sheet pan. Broil until lightly browned, about 5–7 minutes.

Flip the bread slices, sprinkle with Gruyère, and return to the broiler until the cheese is fully melted, bubbly, and lightly browned.

Assemble the turkey and cheese sandwich by layering the turkey, cheese, lettuce, and tomato between the sourdough slices.

Serve the soup with cheesy crostini alongside ½ turkey and cheese sandwich and cucumber water.