Melting Moments with Custard Buttercream

Melting moments are small, pale, exceptionally short biscuits that live up to their name: they collapse to soft crumbs almost the instant they hit your tongue, held together by cornflour and custard powder rather than gluten. Sandwiched in pairs with a soft custard buttercream, they are a staple of British and Australian baking tins, and utterly plain by design. My twist runs a sharp thread of lemon through the custard filling, so the sherbet tang of the fruit lifts what can otherwise be a very sweet, very buttery mouthful and stops the whole biscuit sitting heavy.

A biscuit and a name with two homes

The phrase “melting moment” as a description of a rich, short biscuit turns up in British and Commonwealth cookery through the early twentieth century, and the biscuit has quietly split into two related traditions. In Britain, melting moments are often the coconut-rolled version, soft rounds of buttery dough dredged in desiccated coconut before baking and frequently topped with a single glacé cherry, sold in bakeries and church-hall cake stalls for generations. In Australia and New Zealand, the more common form, and the one this recipe follows, is a pair of smooth, custard-powder-tender biscuits sandwiched with buttercream, often called yoyos for the way the two flat-fork-marked halves face each other like the two discs of the toy.

What unites both is the deliberate softness. This is a biscuit that set out to be genteel, a thing to serve on a good plate with tea, and the name itself is a piece of marketing that stuck: a biscuit so short it melts in the moment. The custard-powder version owes a particular debt to Bird’s custard powder, the cornflour-and-colouring blend invented by Alfred Bird in Birmingham in 1837 for a wife who could not eat eggs, which by the twentieth century had become a fixture of British and Antipodean cupboards and found its way into biscuits, cakes and buttercreams far beyond its original use as a pouring custard.

The yoyo in particular became a country-show and school-fete standard across Australia, the sort of biscuit judged by how cleanly it holds its fork marks and how tender it eats. It belongs to the same family of soft, sandwiched, buttercream-filled British biscuits as my Viennese whirls with raspberry and buttercream, where the tenderness comes from a different flour trick but the finished idea, two delicate halves glued with cream, is a close cousin.

Why custard powder and cornflour make the texture

The reason melting moments melt is that a good chunk of the flour is replaced with starch that carries no gluten. Custard powder is essentially cornflour with vanilla flavour and a little yellow colour, and both it and plain cornflour dilute the wheat flour’s gluten-forming proteins, so the baked biscuit has almost no chew or structure and simply crumbles. That yellow colour and gentle vanilla scent are the custard powder’s contribution to flavour, giving the biscuit a faint eggy-custard warmth without a single egg in the dough. Get the ratio wrong by using all plain flour and you bake a firm, snappy biscuit that has missed the entire point.

Creaming the butter and icing sugar properly matters more than it looks. Beating softened butter with icing sugar for a full three minutes works air into the fat, which lightens the finished biscuit and helps it stay tender, and icing sugar rather than caster keeps the crumb fine and smooth because it dissolves completely rather than leaving any grain. The dough comes together soft and a touch greasy to the hand, which is correct; resist adding extra flour to firm it up, because that stiffness is what tenderness feels like before baking.

Portion the dough into balls of about 15g, sit them well apart, and press each one with a floured fork, which both flattens the biscuit to an even thickness and gives the traditional ridged top. Bake low and slow at 170C fan until the biscuits are just set and only barely golden at the very edges; these should stay pale, because colour here means the butter is browning and the delicate flavour is being lost. They firm up considerably as they cool, so they will feel alarmingly soft coming out of the oven and need five minutes on the sheet before they are stable enough to move.

The lemon custard buttercream

The classic yoyo filling is a plain custard buttercream, butter beaten with icing sugar and custard powder until pale and fluffy, and it is lovely in a mild, nursery-tea way. My change is to fold lemon zest and a little juice through it, which brightens the whole biscuit and gives the palate something to push against. The zest carries the fragrant oils, and a small amount of juice adds the acidity, so together they cut cleanly through the double richness of a butter biscuit filled with buttercream. Two teaspoons of juice is enough to season the filling without slackening it; add much more and the buttercream loosens and weeps.

Beat the filling butter well before adding anything else, then work in the icing sugar, custard powder, zest and juice until it is smooth and pale enough to hold a piped ridge. If the day is warm and the buttercream feels too soft to pipe, a few minutes in the fridge firms it up; if it is too stiff, a teaspoon of milk loosens it. Pair the cooled biscuits by size before you fill them, since baking rarely produces perfectly matched rounds, and a well-matched pair sandwiches far more neatly than two mismatched ones squeezed together.

The custard powder in the filling as well as the dough is the detail that ties the biscuit together, doubling down on that gentle vanilla-custard flavour so the sandwiched whole tastes coherent. The same principle of running an acid through a rich filling shows up in my empire biscuits with jam and icing, where it is the sharp jam doing the cutting instead of citrus, and both biscuits are better for it.

The recipe

Heat the oven to 170C fan and line two sheets with parchment. Beat 175g softened butter, 50g sifted icing sugar and 1 teaspoon vanilla until pale and fluffy, about 3 minutes. Sift in 150g plain flour, 40g custard powder, 40g cornflour and a pinch of salt, and mix to a soft dough. Roll into 15g balls, space them well apart, and flatten each with a floured fork. Bake for 13 to 15 minutes until just set and barely coloured, then cool on the sheet for 5 minutes before moving to a rack.

For the filling, beat 100g softened butter until pale, then beat in 120g sifted icing sugar, 2 tablespoons custard powder, the zest of 1 lemon and 2 teaspoons lemon juice until smooth and fluffy. Pair the cooled biscuits by size, pipe or spread filling onto the flat side of one, and sandwich with its partner. Rest for 20 minutes to firm before serving.

Tips, storage and variations

The most common failure with melting moments is overbaking, which turns a tender biscuit dry and sandy, so pull them the moment they set even if they look underdone, and trust that they firm as they cool. If your biscuits spread and lose their fork marks, the butter was too soft or the dough too warm; chill the shaped balls for ten minutes before baking on a hot day. Unfilled biscuits keep in an airtight tin for a week, and are best sandwiched no more than a day before serving, since the filling gradually softens the biscuit from the inside.

For variations, a passion fruit pulp folded into the buttercream in place of the lemon gives a more tropical tang, and orange zest with a whisper of cardamom makes a warmer, more Christmassy filling. A little cocoa powder swapped into the dough turns them into chocolate melting moments that pair beautifully with the plain custard cream. If you like this style of soft, short, tender biscuit, my petticoat tails Scottish shortbread works the same buttery register with a snappier, sandier bite for the days you want something to dunk.