The original name for the version of these biscuits that is sold commercially comes from a Beano comic book character called Roger the Dodger, who I believe was quite jammy. If you are feeling adventurous or reckless you could change the jam for another flavour. Apricot, maybe. Roger won’t mind.
For the biscuits
200g cold unsalted butter, chopped
200g plain flour
100g caster sugar, plus more to sprinkle
pinch of sea salt
For the filling
75g unsalted butter, softened
½ vanilla pod, split, seeds scraped out
75g icing sugar, sifted
8 tsp raspberry jam (preferably home-made)
Preheat the oven to 140°C/fan 120°C/gas mark 1. The low temperature is intentional, so the shortbread sets slowly and cooks evenly.
Rub the butter into the flour, sugar and salt in a large mixing bowl until you have a texture like crumbs. Or you can pulse the ingredients together in a food processor instead. Now form it into a dough with your hands (you might need a splash of water to help it come together).
Divide the mix in 2 and lightly shape each into a log about 6cm in diameter (don’t overwork the mixture). Wrap in cling film and chill in the fridge for 1 hour. Once firm, cut each into 8 circles and space them evenly over 2 large baking trays lined with baking parchment, a small distance away from each other as they will spread slightly.
Bake for 35–40 minutes or until a light golden brown. You may need to turn the trays around halfway through to ensure the biscuits cook evenly in the oven.
As soon as the biscuits come out of the oven, cut a hole in the centre of half of them with a 3cm cutter, or the smallest cutter you have. (You can also cut them out once more with a 6cm cutter if you want to tidy up the edges.) Place the baking tray on a cooling rack and leave to cool.
Meanwhile, make the filling. Beat the butter and vanilla seeds in a large mixing bowl (or in a food mixer fitted with the beater attachment), then beat in the icing sugar until thoroughly combined.
Once the biscuits are cool, carefully remove them with a palette knife. Turn the intact biscuits upside-down and gently spread the buttercream over, leaving a space in the middle of each for 1 tsp of jam. Add the jam. Sandwich together with the biscuits with the holes and sprinkle with caster sugar.