• Line two baking sheets with baking paper. (If you don't have baking sheets, you can use shallow baking trays instead).

Make the biscuits

• Tip the butter and sugar into a large mixing bowl and beat with a handheld electric mixer, or wooden spoon, for 3-5 minutes, until pale and creamy. Use a spatula to scrape down the sides of the bowl as necessary.
• Add the egg and 1/2 teaspoon of vanilla extract and beat again until combined.
• Sift in the 240g of plain flour and, using the spatula, mix to form a crumbly dough.
• Lightly flour your work surface with a little of the reserved 25g of flour. Gather the dough together with your hands, tip it out onto the floured surface and knead until smooth. Do not overwork the dough.
• Use a large, sharp knife to cut the dough in half, then shape each half into a flattish disc. Wrap the discs (in film) and chill them in the fridge for (at least) 30 minutes to firm up.
• Remove the dough discs from the fridge and unwrap one of them. Lightly dust your work surface with a little more of the reserved flour and roll out the dough until it is about 3mm thick.
• Use the 8cm fluted cutter to cut out your biscuit shapes, gathering up and re-rolling the trimmings until you have 12 biscuit shapes altogether.
• Using a palette knife, transfer the 12 biscuits to one of the lined sheets, spacing them a few centimetres apart. Repeat steps 6 and 7 for the other half of the chilled dough, to give 24 biscuits altogether (12 on each baking sheet).
• Use the 3cm plain round cutter to stamp out the centres of the 12 biscuits on one of the lined baking sheets (but not the other). Place both baking sheets in the fridge for 30 minutes to chill the biscuits. Meanwhile, heat the oven to 180°C/160°C fan/Gas 4.
• Bake both sets of chilled biscuits for 13-15 minutes (watch closely from around 8 minutes as they may bake more quickly - mine took 10 minutes!), until the edges start to turn a pale golden colour. Leave to cool on the baking sheets for 5 minutes, then transfer them to a wire rack to cool completely.

Make the filling

• Make a buttercream. Tip the butter into a clean bowl and add 1/2 teaspoon of vanilla extract. Using a handheld electric mixer, or a wooden spoon, beat for 3-5 minutes, until soft and smooth.
• Add half the icing sugar and beat well, then add the other half and beat again. Keep beating, scraping down the sides of the bowl as necessary, until the buttercream is light and fluffy.
• Transfer the buttercream to a small bowl and cover it with baking paper until you're ready to use it.

To assemble

• Turn the complete biscuits (without a hole) bottom side up. Spoon 1 tablespoon of buttercream into the centre of each, spreading it out in an even layer and leaving a small border around the edge.
• Top each of these biscuits with 1 teaspoon of jam and spread this out over the buttercream, leaving a border of buttercream around the edge of the jam.
• Top each jammy biscuit with a biscuit ring, pressing down gently to sandwich the filling between the two. Set aside while you make the decoration.

  (Don't spread the jam too close to the edge of the biscuit otherwise it will ooze out when you sandwich the biscuits together).

To decorate

• Place a small saucepan of water over a low heat and bring the water to a simmer. Place a heatproof bowl on top of the pan and add the chocolate. Once the chocolate starts to melt, stir gently to melt completely, then immediately remove the bowl from the heat. Take care not to overheat the chocolate.
• Leave the melted chocolate to cool for 5 minutes, then carefully spoon it into the small piping bag, making sure it gets all the way to the bottom.
• Place the biscuits back on the wire rack, positioned over a sheet of baking paper. Snip a tiny hole in the end of the piping bag and pipe lines back and forth over one half of each sandwiched biscuit, piping across the hole in the middle.
• Leave the white chocolate piping to set for 15 minutes, then serve and enjoy!