Make the filling: Mix cream cheese, crab, garlic powder, sugar, Worcestershire, salt, and spring onions until well combined. Pulse briefly in a food processor for a semi-chunky texture, if desired.
Prepare the pan: Preheat oven to 350F (175C). Brush a 9×13-inch baking dish with melted butter. Keep phyllo covered with a damp towel while working.
Assemble: Layer one sleeve of phyllo in the pan, lightly buttering every 2-3 sheets. Spread filling evenly over the phyllo. Top with the second sleeve, again buttering every few sheets. Finish with remaining butter, fully coating the top.
Cut and bake: Using a sharp knife, cut into diamonds or squares before baking. Bake for 40-45 minutes, until golden brown and crisp.
Serve: Cool for 10-15 minutes before serving. Serve warm with sweet Thai chili sauce on the side or drizzled over top.
