1.Process flour, butter and sugar until crumbly. Add egg yolk; process with enough milk until mixture forms a ball. Knead dough on lightly floured surface until smooth; cover, refrigerate 1 hour.
2.Roll dough between sheets of baking paper to form 20cm x 30cm (8-inch x 12-inch) rectangle; remove top sheet of paper. Spread dough evenly with hazelnut spread; sprinkle with hazelnut meal. Using paper as a guide, roll dough tightly from long side to enclose filling. Enclose roll in plastic wrap; refrigerate 30 minutes.
3.Preheat oven to 180°C/350°F. Grease oven trays; line with baking paper.
4.Remove plastic from dough; cut roll into 1cm (½-inch) slices. Place slices on trays 2.5cm (1 inch) apart. Bake about 20 minutes. Stand pinwheels on trays 5 minutes; transfer to wire rack to cool.
Make dough up to end of step 2 and freeze for up to 2 months. Thaw at room temperature, for 1 hour before slicing and baking. If you don’t have hazelnut meal in your pantry, it’s easy enough to grind the nuts yourself for the small amount required here. Toast the nuts briefly in a small frying pan, stirring constantly. Wrap in a tea-towel and rub off their skins. Process in a coffee- or spice-grinder (or mini food processor) to a coarse meal consistency.