- 2 1/2 pounds Japanese, Persian, or English hothouse cucumbers
- 2 tablespoons (1/4 stick) unsalted butter, melted
- 3/4 cup labneh (Lebanese yogurt cheese) or Greek-style yogurt
- 3/4 cup mayonnaise
- 3 tablespoons salt-packed capers, rinsed well, roughly chopped
- 1 garlic clove, finely chopped
- 2 tablespoons finely chopped fresh flat-leaf parsley
- 2 tablespoons finely chopped fresh mint leaves
- 1 tablespoon (or more) fresh lemon juice
- Fine sea salt and freshly ground black pepper
- 2 9×7 inch loaves focaccia, halved horizontally, or 8 ciabatta rolls
- Extra-virgin olive oil
- Preheat oven to 400°. If using English cucumbers, split lengthwise and remove seeds (leave other varieties whole). Arrange cucumbers on a parchment paper-lined baking sheet. (If using English cucumbers, arrange cut side down.) Brush with melted butter. Roast cucumbers until crisp-tender, about 15 minutes. Transfer cucumbers to a paper towel-lined plate; chill until cold.
- Cut Japanese or Persian cucumbers lengthwise in half. Cut hothouse cucumber halves lengthwise in half. Slice crosswise into 1/4 inch-thick pieces. Whisk labneh and next 5 ingredients in a large bowl. Stir in sliced cucumbers and 1 tablespoon lemon juice. Season filling to taste with salt, pepper, and more lemon juice, if desired.
- Brush cut sides of focaccia or rolls with olive oil; place on a baking sheet and toast in a 400° oven until just crispy and lightly browned, 3-5 minutes. Divide filling among focaccia bottoms, cover with tops, and cut each into 4 sandwiches (or divide filling among rolls).