(about ½ sheet) butter puff pastry, well chilled (see note; freeze remaining)
Crème fraîche, to serve
Juice of 1 orange
mandarins, segments removed, plus mandarin rind, finely grated on a Microplane, to serve
Preheat oven to 200C and line an oven tray with baking paper. Scatter sugar over a piece of baking paper, place pastry on top and roll out to 3mm thick. Trim to a square, scatter remaining sugar evenly over the top, then roll 2 opposite sides inwards to meet in the centre and press gently to join. Transfer to a tray and place in the freezer for 10 minutes to firm up, then carefully cut into 1cm slices, place on prepared tray and bake until bases start to turn golden (4½-5 minutes), then turn with a metal spatula and bake until golden and crisp (3½-5 minutes; be careful, hot caramel will burn). Transfer palmiers on baking paper to a wire rack to cool and for sugar harden (5 minutes).
Place sugar and orange juice in a saucepan and bring to the boil, stirring to dissolve sugar. Transfer to a bowl placed over ice and stir to cool (5 minutes), then add mandarin segments. Serve mandarins and syrup with palmiers, top with a spoonful of crème fraîche and scatter with grated mandarin rind.