1Prepare the Filling: Melt butter in a large pan over medium heat. Add the onion and the white parts of the green onions; sauté for 4–5 minutes until softened.
2Add imitation crab meat, flour, heavy cream, cream cheese, dashi powder, white pepper, soy sauce, and lemon juice. Cook until thickened and glossy, then cool completely.
3Assemble the Hand Pies: Roll out puff pastry sheets on a lightly floured surface. Cut into squares. Place a heaping tablespoon of filling in the center of each square. Brush edges with beaten egg wash, fold into triangles or rectangles, seal securely.
4Arrange pies on a lined baking sheet. Brush with egg wash and sprinkle sesame seeds on top.
5Bake at 200°C (392°F) until golden and crispy, about 18–22 minutes. Let cool slightly before serving with lemon wedges and chopped fresh parsley.