Grapefruit shortbread with marshmallow icing

A tangy grapefruit shortbread with a sticky marshmallowy icingToday I am featuring a recipe that my grandmother was famous for. They are a universal favourite –the melting moment, or yo-yo. A shortbread that always, always receives compliments and requests for the recipe. My grandma used a secret ingredient – that of custard powder, to give the shortbreads a vanilla, soft, melt-in-your-mouth texture.

Usually I save this recipe for the Christmas period. They are simple and quick to make, and so fail-proof, they’re fantastically seasonal. However, faced with some grapefruits gifted to me by my neighbour, and wanting to bake something different with them, I decided to jazz up my grandma’s shortbread recipe with a new twist.

A tangy grapefruit shortbread with a sticky marshmallow icing

An unexpected combination: grapefruit, shortbread and marshmallow, but if you make the recipe below, I think you will find that it works like a charm!

A tangy grapefruit shortbread with a sticky marshmallow icing

Grapefruit shortbread with marshmallow icing

  • Servings: approx. 20
  • Print


For the shortbreads:

  • 120g unsalted butter, softened
  • 60g caster sugar
  • 60g custard powder
  • 120g plain flour
  • Zest of one grapefruit

For the icing:

  • 30g butter
  • Juice of one grapefruit
  • 130g marshmallows
  • ¼ cup caster sugar


  1. Preheat oven to 180° Celsius. Grease a baking tray with spray oil.
  2. Cream butter and sugar with beaters or a stand mixer until light and fluffy.
  3. Add custard powder, flour and grapefruit zest, and beat until mixture forms a dough.
  4. Using a rolling pin, roll dough until it is approximately ½ cm thick. You may need to dust the worktop and the rolling pin with a little extra flour so that it doesn’t stick.
  5. Use a 4cm diameter scone cutter to cut the biscuits. Continue to roll out the dough until it is all used.
  6. Place the biscuits on the tray and bake in the oven for 15-20 mins or until golden. Once baked, leave on the tray for 5 mins to cool, and then remove to a wire rack to cool completely.
  7. To make the icing, melt the butter, grapefruit juice and marshmallows in a small saucepan on a low heat. Once melted and combined, add the sugar and continue to cook and stir until sugar has dissolved.
  8. Place the icing into a clean bowl and put into the fridge for at least an hour to cool and set. The icing should become sticky and not run off a spoon.
  9. Once the icing is sticky, spoon it into a piping bag and pipe onto the cooled biscuits. Leave to cool and set completely.



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