In a saucepan, whisk milk, sugar, and cornstarch until smooth.
Cook over medium heat, stirring constantly, until thick and creamy.
Remove from heat and stir in vanilla extract. Let cool slightly.
Layer banana slices at the bottom of serving cups.
Pour warm custard over the bananas and smooth the top.
In a pan, melt butter and toast shredded phyllo dough until golden and crispy.
Let it cool slightly, then sprinkle generously over the custard cups.
Chill for at least 20 minutes before serving for best texture.
