In a medium sized bowl, whisk together the egg yolks, sugar and four. Set aside.
In a medium saucepan, heat together the milk, cream and vanilla extract and bring to a light simmer.
Remove from the heat and pour into the egg and sugar mixture, whisk swiftly.
Add the custard mixture back into the saucepan and return to the heat. Whisk the custard until it thickens. Pour the custard into a bowl and cover with cling film so it is touching the top of the custard. Refrigerate until cooled.
Meanwhile, whip the cream until soft peaks have formed.
To assemble, line the bottom of the cooked tart shell with the custard mixture. Top with the whipped cream, sliced banana and drizzle with caramel sauce if desired.