Chocolate orange cupcakes

I had been eyeing up this recipe in the Hummingbird Bakery Cake Days book for a while and I finally got round to making them a few days ago.

The icing is absolutely delicous, although I didn't pipe it particularly well. I would quite happily and greedily eat an entire bucket of this icing. It's like a Terry's Chocolate Orange in liquid form. Can't get much better really.

However I wasn't bowled over by the cupcake itself. They came out the oven beautifully risen but when I came back to them a few minutes later they had sunk. Not in an undercooked way, they were definitely cooked, but they went flat and quite dense. The icing outshone the sponge which I found just a bit too heavy in texture although the flavour was good. This has happened to me before with Hummingbird cupcake recipes. Am I alone with this? Are Hummingbird Bakery cupcakes maybe denser and milkier in texture (more like a muffin) or have I baked them incorrectly? Despite my concerns my Dad absolutely loved them. In fact he thought they were the best cupcakes ever so it's probably just personal preference.

Chocolate orange cupcakes

Recipe from The Hummingbird Bakery Cake Days cookbook

For the sponge:
70g (2 1/2oz) unsalted butter

210g (7 1/2oz) caster sugar

105g (3 1/2oz) soft light brown sugar

2 large eggs

1 tsp vanilla essence (I used extract)

1 tbsp finely grated orange zest

255g (9oz) plain flour

50g (1 3/4oz) cocoa powder

1/4 tsp salt

240ml (8 1/2 fl oz) whole milk

For the icing/frosting:

600g (1lb 5oz) icing sugar

100g (3 1/2oz) unsalted butter, softened

250g (9oz) full fat cream cheese

60g (2oz) cocoa powder

3 tsp finely grated orange zest

Candied orange peel, thinly sliced to decorate (I used edible glitter and hearts instead)

Preheat the oven to 190C/375F/Gas 5 and fill a muffin tin with muffin cases. Cream together the butter and both types of sugar until pale and fluffy, then beat in the eggs one at a time on a medium speed, followed by the vanilla essence and orange zest. Sift together the remaining ingredients, then add to the creamed mixture in three batches with the milk, alternating between each and mixing on a low speed. Scrape down the sides of the bowl after each addition, and once everything has been incorporated, raise the speed to medium and continue beating until the batter is well mixed and smooth. Divide the mixture between the paper cases, filling each up to two-thirds full. Place in the oven for 18-20 minutes or until the sponges spring back when gently pressed. Allow to cool for a short while in the tin, then transfer to a wire rack to finish cooling.

To make the frosting, whisk the icing sugar with the butter on a low speed (or by hand otherwise it's seriously messy!) until crumbly in texture and no large lumps of butter remain. Add the cream cheese and cocoa powder and continue to mix on a medium speed until the frosting is smooth and light. Add the orange zest and stir in by hand. Smooth the icing on by palette knife or pipe with a star nozzle.