01 - Preheat oven to 400°F. Line baking sheet with parchment paper.
02 - Heat olive oil in skillet over medium heat. Add spring onions and garlic; sauté 1–2 minutes until fragrant.
03 - Add spinach and cook until wilted if using fresh or heated through if using frozen. Remove from heat and cool several minutes.
04 - Combine crumbled feta, cream cheese, cooked spinach mixture, nutmeg, salt, and pepper in bowl. Mix thoroughly.
05 - Unroll puff pastry on lightly floured surface. Spread spinach and feta mixture evenly over pastry, leaving 1/2 inch border along one long edge.
06 - Starting from opposite long edge, tightly roll pastry like jelly roll. Brush border with beaten egg to seal.
07 - Slice roll into 16 equal pieces. Arrange pinwheels cut-side up on prepared sheet, spacing slightly apart.
08 - Brush tops with beaten egg and sprinkle with sesame or nigella seeds if desired.
09 - Bake 18–20 minutes until puffed and golden brown.
10 - Cool slightly before serving warm or at room temperature.