Preheat oven to 190°C (170°C fan) mark 5. To make the biscuits, using a handheld electric whisk, beat together butter, icing sugar and vanilla in a medium bowl until light and very fluffy. Sift in the plain flour and cornflour, and beat until just combined.
Step 2
Split mixture in half. Into one bowl, sift the cocoa powder and beat to combine. Line 2 large baking sheets with baking parchment.
Step 3
Fill one side of a piping bag (fitted with a 1cm closed star nozzle) with the plain mixture, using your hands to shape it. Squash the chocolate mixture into the other side of the piping bag.
Step 4
Pipe 2cm swirls on to the lined sheets, spacing apart. The mixture will be very stiff – it helps if you seal the piping bag and squeeze from the middle rather than the top. Chill for 20min until firm. Bake for 15min until lightly golden. Cool on trays for a few minutes, then transfer to a wire rack to cool completely.
Step 5
To make the filling, in a large bowl, beat together butter, icing sugar and milk with a handheld electric whisk. Beat in the grated chocolate. Pipe or spread chocolate over bases of half the biscuits, then sandwich together with remaining biscuits. Serve.
Get Ahead: Keep sandwiched biscuits in an airtight container at room temperature for up to 3 days.
The GH Kitchen Team are Good Housekeeping’s resident recipe developers and all-round food obsessives. GH Kitchen Director Sarah Akhurst is our resident hosting pro and loves nothing more than putting on a foodie feast for friends. Our GH Kitchen Manager Linzi Pucino is our very own Italian food expert (originally hailing from the North East of Scotland!) and can be found working her way through midweek recipes that cover all bases, from haggis to ragu! Our Kitchen Editor Nadine Brown loves digging into the stories behind her favourite foods and enjoys applying her eclectic tastes to more modern, flavour-forward recipes - just don't give her too much chilli! Our Junior Food Content Produce Frankie Prichard combines a love of beautiful presentation and flavour-led, seasonal cooking in her recipe development, along with a passion for bringing people together through food. With a wealth of professional kitchen experience between them, they’re dedicated to ensuring every Good Housekeeping recipe is the best it can be, so you can trust they’ll work every single time
