Preheat oven to 400°F (200°C). Cut the top off the garlic head to expose the cloves, drizzle with 1 tablespoon olive oil, wrap in foil, and roast for 40 minutes until soft and golden. Let cool completely.

While garlic roasts, soak the bread slices in a small bowl of water for about 5 minutes until soft, then squeeze out the excess moisture with your hands.

Squeeze the cooled roasted garlic cloves out of their skins directly into a high-powered blender.

Add the blanched almonds, soaked bread, sherry vinegar, salt, and about 1/2 cup of the ice water to the blender.

Blend on high speed until a smooth, thick paste forms.

With the blender running on low speed, slowly drizzle in the 1/2 cup extra virgin olive oil to create a creamy emulsion.

Add the remaining ice water gradually while blending until the soup reaches a milky, pourable consistency.

Transfer to a pitcher and chill in the refrigerator for at least 1 hour to allow flavors to meld.

Serve very cold in bowls, garnished generously with the halved green grapes and a final drizzle of olive oil.