Prep the ingredients for blending: Slice off the little stem end of each cucumber and coarsely chop them. Juice the lemon or lime; measure out 2 tablespoons and set aside for later. Peel and chop the shallot. Seed and dice the optional jalapeño. Mince the chives or scallions for garnish.

In a high-speed blender combine the cucumbers, lemon juice, shallot, jalapeño (if using), spinach, 1 cup of the yogurt, herbs, salt, pepper, and ¼ cup of the olive oil and blend until smooth, then chill until very cold, at least 30 minutes to an hour.

While the soup chills, toast the two slices of bread, then cut them into ½-inch cubes. Fry in a skillet tossed with 2 tablespoons olive oil until browned and crispy; transfer to a kitchen towel to drain and set aside.

Stir together the remaining Greek yogurt and lemon juice to thin it out (adding a tablespoon of water if needed; it should be the consistency of thick heavy cream).

Serve the chilled soup in shallow bowls garnished with croutons, minced chives or scallions, herbs, edible flowers, a drizzle of thinned yogurt, and a drizzle of extra virgin olive oil.