Melt butter and add leeks.
Cook about 8 mins.
In a bowl make the custard by mixing cream and eggs.
Stir in cooled off leeks, cheese, salt/pepper, pesto, prosciutto.
Pour this into the crust.
Cover loosely with nonstick foil and bake 45 mins.
Remove foil and bake for an additional 10 minutes.
Let cool 10 mins and cut into slices.
Goes well with a nice salad!