Step 1Thoroughly butter one side of each bread slice. Arrange slices of halvah in a single layer on unbuttered side of one slice of bread. Lay banana slices in single layer over halvah and drizzle silan over bananas. Sprinkle a little chopped chocolate over, if desired. Cover with second slice of bread, butter side out. Place in panini press and toast until crisp and golden brown. Or, place in a heated skillet and weight with a second pan. Toast over medium heat until golden brown and crisp, flipping the sandwich halfway through toasting, 7 to 10 minutes total. Cool the sandwich slightly before cutting in half. Embellish with a dollop of crème fraîche or labneh, if desired. Serve the sandwich warm or at room temperature.