Step 1The night before, put the blanched almonds into a bowl, cover with the mineral water and soak overnight.
Step 2Bring 2 cups of water to a boil in a small pot. Add the garlic and boil for 1 minute, then drain the garlic and cool.
Step 3Place a colander over a large bowl and line it with cheesecloth. Drain the soaked almonds, reserving the soaking liquid, and put them in a blender or food processor; this will need to be done in batches. Add the garlic, reserved soaking liquid, three-fourths cup of the sherry vinegar and 2 1/2 cups of the olive oil in batches with the drained almonds and pulse until smooth. Pour the soup into the colander as it is pureed. Once most of the liquid has passed through the colander, gather the cheesecloth around the remaining solids and squeeze gently to release as much of the liquid as possible. Discard the solids. This makes about 6 cups soup. Pour the soup through a fine sieve into a pitcher and chill for 30 minutes.
Step 4To serve, divide the fig pieces and Marcona almonds among soup bowls. Pour in the cold soup, sprinkle with chopped chives and drizzle with the remaining 1 tablespoon vinegar and 2 tablespoons olive oil.