113gunsalted buttersoftened but still cool (½ cup / 1 stick)
90gcaster sugar (or granulated sugar)(⅓ cup + 2 tbsp)
1large egg yolkat room temperature
1tspvanilla bean paste or vanilla extract
20mlwhole or 2% milk(1 tbsp + 1 tsp)
For the Custard Filling
75gunsalted buttersoftened (5 tbsp + 1 tsp)
100gpowdered sugar(¾ cup + 1 tbsp + 1 tsp)
20gBird’s Custard Powder(2 tbsp + 1 tsp)
15mlwhole or 2% milk(2½–3 tsp)
½tspvanilla bean paste or vanilla extract
Equipment
Baking sheet
Parchment paper
Rolling Pin
Wire cooling rack
Custard cream cutter and stamp optional
Kitchen scale optional, but recommended
Method
Make the Biscuits
Beat the butter and sugar together for 1½–2 minutes, until smooth and creamy but not very pale or fluffy.
Add the egg yolk and vanilla and beat just until combined.
In a separate bowl, whisk together the all-purpose flour and custard powder. Add to the butter mixture and mix in until crumbly and beginning to come together.
Add the milk and mix just until a dough forms. Avoid overmixing.
Flatten the dough into a disc, wrap well, and refrigerate for 45–60 minutes.
If the chilled dough feels very firm or cracks when you begin rolling it, let it sit at room temperature for 5–10 minutes.
Roll the dough to about 4 mm thick (roughly the thickness of two stacked US nickels) on a surface very lightly dusted with custard powder. Cut with a custard cream cutter or small rectangular cookie cutter. If using a stamp, press the design firmly into each biscuit.
Transfer the biscuits to a parchment-lined baking sheet and refrigerate for 10–15 minutes, or until firm.
Preheat the oven to 340°F conventional. Bake on the middle rack for about 13-15 minutes, until the tops are dry and set and the biscuits remain mostly pale with just a hint of color around the edges.
Leave the biscuits on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.
Make the Custard Filling
Warm the milk until hot to the touch but not boiling.
Whisk in the custard powder until smooth, then allow the mixture to cool to room temperature.
Beat the softened butter until smooth and creamy.
Add the powdered sugar, vanilla, and cooled custard mixture to the butter. Beat until smooth and creamy.
Assemble
Spoon about 1 teaspoon of filling onto the center of the flat side of one biscuit.
Top with another biscuit and press down gently until the filling spreads toward the edges.
Repeat with the remaining biscuits.
Notes
Custard powder: I use Bird’s Custard Powder for its traditional vanilla-custard flavor and pale yellow color.Caster sugar: Caster sugar helps give the biscuits a fine, tender crumb. If you can’t find it, granulated sugar will also work, although the texture may be slightly different.Stamping: A traditional custard cream cutter and stamp gives the classic embossed appearance, but it is optional. A small rectangular cutter works just as well.Filling: This version has a slightly more generous filling than a typical packet custard cream. Depending on how generously you fill the biscuits, you may have a little filling left over.Storage: Store in an airtight container at room temperature for up to 5 days. They are at their best during the first 2–3 days and will gradually soften as they sit.High altitude: This recipe was developed and tested at approximately 8,600 feet in Woodland Park, Colorado. At this elevation, the biscuits baked well at 340°F for 13 minutes.