Preheat your oven to 170°C (150°Fan, gas mark 3, 325°F) and line a baking tray with parchment paper.
Add butter and sugar to a large mixing bowl or food processor and cream together until light and fluffy. Add the egg and vanilla extract and mix until combined.
100 g Butter, 100 g Caster Sugar, 1 Egg, ½ tsp Vanilla Extract
Add flour and custard powder and mix together until thoroughly combined. Use your hands to help bring the dough together.
175 g Plain Flour, 35 g Custard Powder
Gently knead the dough on a lightly floured work-surface until the dough is combined and smooth. Roll the dough into a ball then use your palms to slightly flatten it into a disc shape.Wrap the dough in cling film and leave it to chill in the fridge for 1 hour or freezer for 30 minutes.
Roll the dough into a 3mm (0.3cm) thickness. Lightly flour your custard cream cookie cutter, then use it to cut out pieces of dough, stamp the design and place it onto a lined baking tray. See notes if not using cookie cutter.
Bake in the oven for 12 to 14 minutes or until the biscuits are starting to turn golden brown around the edges. Leave the biscuits to cool down for at least 5 minutes before transferring to a cooling rack.
Custard Buttercream
To make the custard cream buttercream: add butter, icing sugar, milk and custard powder to a large mixing bowl and mix together until combined, smooth and pale in colour.
100 g Icing Sugar, 50 g Butter, 1 tsp Custard Powder, 1 tbsp Milk
Spoon or pipe buttercream over half of the biscuits and top with the remaining un-iced biscuits (design-side up).
Video
Notes
NOTE (hand shaped biscuits): If you’re not using a patterned stamp, divide the dough equally into balls and press the dough down with your fingers or with a fork.
Quick Tips:
The dough will be sticky and soft - that's normal. Make sure you flour your work surface and hands then gently mould the dough into a ball. Continue adding more flour to your hands and work surface until it's no longer sticky.If you don’t have a large enough tray to bake all 24 biscuits at once, you can bake them in batches. Simply divide the dough into two and keep the second batch of dough in the fridge until you’re ready to bake it. Roll the second batch into shapes just before placing them in the oven for best results.Chilling the dough isn't 100% necessary, but it's vital in helping the biscuits keep its shape and design whilst baking in the oven. In addition, with proper chilling, the dough is less likely to stick to the cookie cutter. If you're not imprinting a design onto the biscuits then you don't need to chill it.Make sure you roll out the dough roughly 3mm (0.3cm) thick, otherwise if the dough is not thin enough, the biscuits will lose the custard cream pattern imprinted onto them. It will still taste nice, just won’t look as amazing.I used a food processor when making this custard cream recipe, simply because it takes less time. However, you can also make these biscuits by hand. When combining the butter and sugar together, use the ‘rub-in-method’ by rubbing the butter and sugar together using your fingertips.