Preheat your oven to 350°F (175°C) and place the unbaked pie shell on a baking sheet.
In a blender, combine sugar, flour, and salt. Pulse briefly to mix.
With the blender running on low, slowly pour in the warm milk until the mixture is smooth and frothy.
Add melted butter, vanilla, and egg yolks. Blend just until fully incorporated—do not overmix.
Pour the custard into the pie shell. Bake for 45–50 minutes or until the center is set but still jiggles slightly.
Remove from oven and cool on a wire rack for 1 hour, then chill in the refrigerator for at least 2 hours.
Before serving, dust with grated nutmeg and top with a dollop of whipped cream.