Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4 and grease a 12 hole donut tins (or two 6 hole ones) with the butter
In a bowl mix together the milk, eggs, vegetable oil, caster sugar and the zest of the lemons
Sieve in the self raising flour and whisk until a smooth batter forms
Divide the batter between the tins. You can put the batter into a piping bag to make it a bit neater to dispense into the trays, but you can do it with a spoon too, or pour into a jug
Bake them for 12 minutes or until they spring back when you press your finger into them, then remove them from the tin (I use a spoon to prise them out) and leave to cool
Make the white icing by mixing the ingredients together
Spread the icing on top of the donuts with a palette knife or spoon
Make the yellow icing by mixing the ingredients together, put it into a piping bag and drizzle it over the donuts
Add some sprinkles if you like
They are best the day they're made, but you can store leftovers in an airtight cotainer and eat within 3 days