Key Lime Mousse Cake

The title is not quite correct because I couldn't find any Key limes! I've made this cake before using oranges, which were the fruit used in the original recipe.It's  from Woman's Weekly magazine, but when I don't know, as it's in my recipe folder. I thought I'd try it with limes, and it turned out well. It's a thick layer of mousse, and it's definitely a dessert cake, rather than a cake to have with a cuppa.
I haven't used the original cake recipe either this time, as I wanted to make a Victoria sandwich.

175g butter
400g caster sugar- 175g for the cake
3 eggs
175g sr flour
1 tspn baking powder
400ml double cream
250g mascarpone cheese
juice and rind of 5 limes
juice of a small orange
1 tbspn gelatine powder
icing sugar to dust
if you want the filling really green, you can use a few drops of green colouring, which I did.

Preheat oven 160C/gas 3
Grease and line a 23cm springform tin.
Beat the butter and 175g of the sugar together till it's creamy and fluffy using a hand mixer. Then add the eggs one at a time, beating between each one. Stir in the flour and baking powder gently and then spoon the mixture into the tin.
Bake for 30-35 mins. Leave the cake in the tin for 5 mins and then turnit onto a wire rack.
For the filling - beat the remaining 225g of sugar with the cream, mascarpone, lime juice and zest and the orange juice to a smooth cream using a hand mixer.
Put 2 tbspn of water in a bowl over a half full pan of simmering water. Sprinkle over the gelatine and stir till it's dissolved. Don't overheat it or the gelatine won't set properly, as I discovered the first time I made it!
Stir the gelatine into the filling mixture and add the green colouring if you want. Beat the mixture again.
Cut the cake in half (horizontally!), clip the side back on the cake tin and put the bottom of the cake in the tin. Spoon the filling on top then put on the top layer of cake. Put in the fridge for 2 hours, then put onto a plate and dust with icing sugar.

I'd forgotten just how much filling there was, and I think maybe I'll try just half the quantity next time.
The mousse laye is refreshing and luxurious, but I think its a bit overwhelming. I'd like a bit more cake.
I like the idea of this cake, and think I'm going to try it with raspberries next time.