Preheat the oven to 170/150 fan/325/gas 3. Line a 12 cup muffin pan with paper cases.
Chop the cavolo nero leaves into bite sized pieces and boil or steam for a few minutes until tender. Refresh by running under cold water, then drain and squeeze out any excess moisture. Chop finely. Puree it with a hand blender - it will be a bit stringy, but you want it to be as smooth a paste as possible to get the best colour. If necessary, add the orange juice to make it easier to puree, then set aside.
In large bowl, cream the butter and sugar with an electric mixer until light and fluffy. Beat in the eggs, one at a time, and beating each one in well, then beat in the cavolo nero, vanilla, orange juice and zest. The batter may split but it will come together when the flour is added.
Sift in the flour, baking powder and salt, and stir gently to combine.
Fill the muffin cups three-quarters full with the batter and bake for 20 minutes, or until a skewer inserted in the middle comes out clean. Leave to cool in the pan for 10 minutes, then turn out onto a wire rack and leave to cool completely.
In a large bowl, cream the butter and sugar with an electric mixer until fluffy, then add the icing sugar and beat until thick. Add enough of the orange juice to make it a frosting consistency - you may not need all of it. Store in the fridge until ready to use.
Spoon into a piping bag and pipe over the cooled cupcakes.
Please enjoy my recipe! Jane | hedgecombers.com