1. Make the pickled grapes: In a large saucepan set over high heat, boil the water, sugar and vinegar until the sugar is dissolved, about 1 minute, stirring occasionally. In a large bowl, add the grape halves, pour the vinegar mixture over the grapes and set aside to cool completely. Use a slotted spoon to remove the grape halves and set aside.

2. Make the ajo blanco: In a large bowl, cover the bread cubes with ½ cup of water and set aside for 20 minutes. Drain the bread and squeeze out the extra liquid, then place the bread in a blender. Add the almonds, garlic and ¾ cup of water and purée into a smooth paste, adding enough of the remaining ½ cup of water to yield a very smooth mixture. Add the olive oil in a slow and steady stream to emulsify the sauce. Pour into an airtight container, stir in the vinegar, season with salt, cover with plastic wrap and refrigerate.

2. Make the scallops: In a small saucepan set over medium heat, heat 2 teaspoons of olive oil. Add the celery, cucumber and almonds and cook, stirring often, until warmed through, about 1½ minutes. Add the pickled grapes, then stir in the sherry vinegar and salt and turn off the heat.

4. Season both sides of the scallops with salt. Heat a medium skillet over medium-high heat until nearly smoking, 1½ to 2 minutes. Add the remaining 2 teaspoons of olive oil and the scallops and cook until golden brown, about 3½ minutes. Turn the scallops over and cook on the other side until golden brown, about 3½ minutes longer. Turn off the heat and set the pan aside.

5. Spoon 3 tablespoons of the ajo blanco in each of 4 shallow bowls. Divide the grape mixture over each serving of ajo blanco, top with 4 scallops, drizzle with olive oil and serve.