Prep the pan and oven: Heat the oven to 350°F (175°C).
Lightly butter a 9- or 10-inch round cake pan, springform, or a similar shallow baking dish.
Get the phyllo ready: Unwrap the thawed phyllo and keep it under a barely damp towel to prevent drying. Don’t stress if sheets tear.
Ruffle the sheets: Take one sheet and gently scrunch it lengthwise into a loose ribbon. Coil it into the pan, starting along the outer edge.
Repeat with more sheets, working inward to create a spiral or concentric circles. Fill the pan snugly, leaving some airy gaps for the custard to soak in.
Butter the ruffles: Drizzle the melted butter evenly over the ruffled phyllo, lifting gently to let it trickle between layers. Sprinkle 2 tablespoons of sugar over the top for extra crispness.
Pre-bake for crunch: Bake the dry, buttered ruffles for 15–18 minutes until lightly golden and crisp.
This prevents soggy layers later.
Make the custard: While the phyllo bakes, whisk the eggs, remaining sugar (about 1/2 cup plus 2 tablespoons), salt, and vanilla. Warm the milk and cream in a small saucepan until just steamy, not boiling. Slowly whisk the warm dairy into the egg mixture.
If you like, add citrus zest.
Add custard to the ruffles: Pull the pan from the oven. Slowly pour the custard over the ruffles, aiming for even coverage so it seeps throughout.
Bake until set: Return the pan to the oven and bake 25–35 minutes, until the custard is mostly set and the top is deep golden. The center should jiggle slightly, like set gelatin.
Finish and cool: Let the pie rest 15–20 minutes.
Dust with powdered sugar and a light pinch of cinnamon if you like. Slice into wedges and serve warm or at room temperature.