Line 2 baking sheets with greaseproof paper. Put the butter and caster sugar in a large bowl and beat together using an electric whisk until pale and smooth.
Using a wooden spoon, stir in the flour until the mixture forms a smooth dough. Wrap in cling film and chill in the freezer for 10 minutes.
Dust your work surface with flour and roll out the chilled dough to a thickness of 0.5cm. Using a 4-5cm round cutter, stamp out 24 rounds – you’ll need to re-roll the trimmings. Place on the prepared baking sheets and chill in the freezer for 10 minutes. Preheat the oven to 180°C, fan 160°C, gas 4.
Remove from the freezer and bake for 10-12 minutes. Transfer to a wire rack to cool completely.
To make the filling, beat together the crème fraîche, soft cheese, vanilla and the icing sugar.
Spoon 1 teaspoon of the filling on top of 8 biscuits, then add either a slice of strawberry or 3 of the berries, and top with a little extra filling. Repeat with another 8, then stack these on top. Finally, top with the remaining 8 biscuits, dust with the extra icing sugar