Lime drizzle cupcakes

I recently made these for my neighbours' 58th wedding anniversary. I promise to make something far more splendiferous for their diamond anniversary in a couple of years' time.

Oven temperature
180C

Ingredients
100g butter, kept in a warm place for a couple of hours to soften it slightly
125ml caster sugar
1 large egg, separated
5ml vanilla extract
175ml plain flour, sifted
10ml finely grated lime zest (or you could use lemon)
5ml baking powder
60ml milk
juice of half a lime

Icing
25ml lime juice
60ml icing sugar

Method

• Cream the butter and sugar together until light and fluffy.
• Whisk in the egg yolk and vanilla.
• Add the sifted flour, zest and baking powder and beat until it is all blended together.
• Add the milk and beat a little before adding the lime juice and beating a bit more for good measure.
• In a separate bowl (with clean blades) whisk the egg white until it forms peaks.
• Fold egg-whites into the rest of the mixture.
• Grease your cupcake pan, or pop a paper cupcake case into each hollow.
• Divide the mixture among about 8-10 cupcake spaces and spread it evenly.
• Bake for about 20-30 minutes or until a skewer comes out clean.
• Cool in the baking tin for a few minutes, then remove and place in a huddle on a flat plate. Poke a few holes in their tops
• Whisk the juice and icing sugar together, then drizzle over the cupcakes.
• Pop the cupcakes onto a cooling rack until cooled.