Quick Raspberry and Blueberry Cake

This one comes from my wife's relative. Simply excellent cake. Some minor changes to the original recipe but generally this works wonders.

Should be enough for about 8

Ingredients:
Base:
150-250 g digestive biscuits, crushed
100 g butter, melted, plus extra for greasing
Cake: 
150 g butter
250 ml sugar
3 eggs
300 ml wheat flour (regular, non-self-raising)
1.5 tsp baking powder
75 ml milk
Topping:
350-400 g raspberries and blueberries (or more. As they say in Estonian, topelt ei kärise)
Icing sugar
To serve:
Ice cream, whipped cream

Mix together the digestives and butter. Grease a 25x35 cm baking tray, then pack the base on the bottom. Put in the fridge to set for about 30 minutes to an hour.

Heat the oven to 200 C. Whisk the sugar together with room-temperature butter. Beat in the eggs one by one, sieve together flour and baking powder and beat into the mixture together with the milk. Pour the dough into the baking tray, smooth it out, and put in the oven to cook for 10-15 minutes.

Take the cake out of the oven, add the berries on top, then put back in the oven for another 15 minutes. Once done, remove from the oven, leave to cool, then top with icing sugar. Serve with ice cream or cream.