Place the berries on a baking sheet in an even layer. Freeze for 1 hour.

To a medium saucepan, add the milk and  sugar over medium heat, bring to a simmer.

While the milk is coming to a simmer, add the eggs to a large mixing bowl. Whisk in the cornstarch until smooth. Slowly drizzle while whisking ⅓ cup of the hot milk into the egg mixture. This will temper the eggs and stop them from curdling or cooking. Add the egg mix to the pan while whisking until thickened. Once the custard has thickened, remove from the heat. If it is too thick, whisk in more milk until it reaches a sauce consistency.  

Stir in the vanilla and mix until well incorporated. If the custard is a little lumpy, just strain through a sieve. 

Serve berries in a bowl and pour over the hot custard. Serve immediately.