In a large saucepan of boiling salted water, cook the cauliflower until tender, about 8 minutes. Drain, rinse under cold water until cool and drain well.

In a blender, combine 1 1/2 cups of cold water with the cooked cauliflower, bread, pine nuts, chopped garlic, sherry vinegar, chopped shallot, 1 cup of the slivered almonds, and the coarsely chopped cucumber; blend until smooth. Add the olive oil and pulse just until incorporated. If necessary, add more water to thin the gazpacho. Season the soup with salt and refrigerate until chilled, about 1 hour.

Preheat the oven to 350 degrees. Spread the remaining 1/4 cup of slivered almonds in a pie plate and toast for about 6 minutes, until fragrant and lightly golden. Ladle the gazpacho into bowls. Garnish the soup with the toasted almonds and the finely diced cucumber and serve.

The white gazpacho can be refrigerated overnight.