Serves: 32 sandwiched biscuits1) Preheat the oven to 160°C/ gas mark 3. Line two baking sheets with greaseproof paper or silicone baking mats.
2) Melt the butter in a small, heavy-bottomed saucepan over a medium heat. Continue to cook, swirling the pan occasionally, until the butter browns lightly and smells slightly nutty, about 15 mins. Transfer the butter to a medium bowl – be sure to get all the tasty brown bits – and cool slightly.
3) Meanwhile, whisk the flour, baking powder and salt in another medium bowl.
4) When the brown butter is cool, whisk in the egg yolk, sugar and vanilla. Stir the dry ingredients into the butter mixture to make a uniform but crumbly dough that looks like wet sand.
5) Scoop out the dough with a small teaspoon (the kind you set the table with, not the ones you measure with). Rock the spoon gently back and forth against the side of the bowl, packing the dough into the spoon, then scrape/slide the spoon against the inside of the bowl to make spoon-shaped biscuits. Trim excess dough with your fingers and slide out onto the prepared pans, preserving their shape. (Try to make sure you form an even number of biscuits, since these sandwich together.)
6) Bake the biscuits until just browned, about 12 to 15 mins. Cool almost completely on the baking sheets, and then transfer the biscuits to a rack to cool.
7) When cool, spread 1/2 tsp jam on the flat side of a biscuit, and then sandwich together with a second biscuits. Repeat until all the biscuits have been paired up. Lightly dust the biscuits with the icing sugar.
Busy Baker's Tips:
The dough can be prepared several hours ahead and stored at room temperature.
Freeze baked biscuit halves wrapped tightly in cling film, followed by aluminium foil, for up to two weeks. When ready to serve, defrost at room temperature and assemble as desired.
Store sandwiched biscuits in an airtight container for up to 3 days. Do not store with crisp biscuits, as moisture from the jam will soften the texture of other crisp biscuits.