Preheat your oven to 180C/350F/Gas mark 4 and line a large muffin pan with cases. I had to bake 2 batches as my largest pan only bakes 12 cupcakes.
Pour the cake mix into a large mixing bowl, add in the milk, melted butter and the egg whites. Mix until everything is well combined.
Scoop the batter into your cupcake cases. I use a large ice cream scoop to keep mine all the same size.
Pop your cupcakes in the centre of your oven and bake for 18-22 minutes. I found 20 minutes hit the sweet spot. Check them with a pick at the 18-minute mark to see if they are done.
Once baked take them out of the oven and allow them to fully cool down on a wire rack.
While the cupcakes are cooling its time to make the buttercream.
Cream the butter, preferably with a stand mixer but an electric hand mixer will work well too. Cream it until it is light and fluffy about 3 - 5 minutes.
While the mixer is on a low-speed add in the icing sugar, beat until everything is well combined. The buttercream will be quite thick but this is ok.
Add in the milk and the almond extract. Be careful with the almond extract as it can be quite potent. Add just a little at a time and taste to make sure you like it. A little goes a long way.
Pipe the buttercream onto the cupcakes and add a few extra sprinkles if you so desire.