Created by ImPat on December 30, 2020
Step 1: Preheat oven to 170°C/150°C fan forced. Line 2 large baking trays with baking paper.
Step 2: Use electric beaters to beat the butter, icing sugar and vanilla in a bowl until pale and creamy.
Step 3: Sift over the flour and custard powder and use a flat-bladed knife in a cutting motion to mix until a soft dough forms and then add the hundreds and thousands and mix until well combined.
Step 4: Roll level tablespoonfuls of dough into balls and place on prepared trays, leaving room for spreading and then use a fork dipped in extra custard powder to press the balls into 4cm rounds (they should be about 1.5 cm thick) and bake, swapping trays halfway through cooking, for 18 minutes.
Step 5: Set aside on trays for 5 minutes to cool slightly then transfer to a wire rack to cool completely.
Step 6: To make the filling, use electric beaters to beat the butter and vanilla in a bowl until pale and creamy and then gradually add the icing sugar, beating constantly, until well combined.
Step 7: Spoon the filling into a piping bag fitted with a 2cm plain nozzle and pipe onto the flat side of half the biscuits (if you don’t have a piping bag you can spread it instead) and then top with the remaining biscuits, flat-side down, to sandwich. Place the extra hundreds and thousands in a bowl and press the side of each biscuit to coat the edge of the filling.