Rhubarb Custard Sandwich Biscuits
Buttery shortbread biscuits with cutout windows sandwiched with homemade rhubarb jam. The dough combines plain flour and custard powder for subtle vanilla-custard notes, while the rhubarb filling is simmered until thick and jammy. Assembly involves piping jam onto solid biscuits, then topping with windowed biscuits for a pretty finish.
Ingredients
- 12 tbsp unsalted butter, cubed
- ¼ cups superfine sugar, for dough
- ¼ cups powdered sugar
- ¼ tsp fine sea salt
- 2 cups all-purpose flour, plus extra for dusting
- 1 ¾ oz custard powderinstant vanilla pudding mixsame qtyflavor_alternative
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- 2 egg yolks
- 1 tbsp vanilla bean pastevanilla extract3/4 tspextract_vs_paste
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- 7 oz rhubarb, trimmed and chopped
- 1 cup superfine sugar, for jam
- ¼ lemon, juiced
Instructions
- 1
Combine rhubarb, superfine sugar, and lemon juice in a pan over medium heat. Bring to a simmer and cook until rhubarb breaks down and releases liquid.
- 2
Blend with a hand blender until smooth.
- 3
Simmer for an additional 5-10 minutes until thick and jammy. Test readiness by running a wooden spoon across the pan base - it should leave a trail without filling in immediately.
- 4
Cool completely, then chill until ready to use.
- 5
Pulse butter, both sugars, and salt in a food processor to a coarse paste.
- 6
Scrape down sides, add flour and custard powder, and pulse to a damp, sandy consistency.
- 7
Add egg yolks and vanilla bean paste, pulse until dough comes together into a ball.
- 8
Add water as needed to bring dough together.
- 9
Wrap dough and chill in the fridge for at least 30 minutes.
- 10
Roll dough on a floured surface to ¼" thickness.
- 11
Stamp out circles using a ¼" round cutter, yielding about 32 biscuits.
- 12
Using the wide end of a piping nozzle (about ⅔") or a small heart cutter, cut centres out of half the biscuits.
- 13
Transfer all biscuits to lined baking sheets and chill for 15 minutes.
- 14
Heat oven to 400°F/350°F fan/gas 6.
- 15
Bake biscuits for 8-10 minutes until golden, or 5-6 minutes for mini biscuits if baking the cut-out shapes separately.
- 16
Cool completely on a wire rack.
- 17
Transfer jam to a piping bag, snip the end, and pipe a small layer onto the plain biscuits, spreading it carefully without reaching the edges.
- 18
Sandwich the windowed biscuits over the jam without pressing firmly.
- 19
Transfer to an airtight container in a single layer and leave to set overnight.
Tips
Test rhubarb jam readiness by running a wooden spoon across the pan base - it should leave a trail rather than filling in immediately.
Chill dough and shaped biscuits before baking to prevent spreading.
When piping jam, don't spread it to the edges to prevent squidge-out when sandwiching.
Let biscuits set overnight in an airtight container to prevent jam leakage when bitten.
Good to Know
Keep in an airtight container for up to three days. Rhubarb jam keeps in a sealed container or jar in the fridge for up to one week.
Rhubarb jam can be made several days ahead and chilled. Dough can be prepared and chilled up to 2 days in advance. Biscuits can be baked 1-2 days ahead and stored in an airtight container before assembly.
Serve at room temperature. Best enjoyed within a few hours of assembly, though they keep for three days in an airtight container.
Common Mistakes
Do not skip the overnight set - this prevents jam leakage when biting into the biscuits.
Do not press biscuits together firmly when sandwiching - gentle placement prevents jam squidge.
Do not spread jam to the edges of the base biscuit - this causes overflow during assembly.
Do not skip the final chill of shaped biscuits before baking - this prevents spreading and maintains the cutout definition.
Substitutions
Dairy-Free Swaps
General Alternatives
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