The Best Cucumber Sandwich

Name: The Best Cucumber Sandwich
Ingredients: 2 medium cucumbers, peeled, seeded, and finely chopped (about 3/4 cup); 2 teaspoons kosher salt, divided; 8 ounces cream cheese, softened; 8 ounces mascarpone cheese; 2 (4-ounce) bunches fresh flat-leaf parsley, chopped (leaves and tender stems only) (about 2 1/4 cups); ½ cup finely chopped red onion (from 1 small onion); 1 medium-size fresh jalapeño (about 1 ounce), seeded and finely chopped; 2 teaspoons chopped fresh dill; 1 teaspoon black pepper