Put the butter, sugar, flour, egg, egg yolk and vanilla bean paste in a bowl and beat with a hand-held electric whisk until light and creamy. Divide among 10 sections of a 12-hole mini muffin tin.
Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for about 15 minutes until risen and just firm. Leave in the tray for 5 minutes, then transfer to a wire rack to cool.
Split the cakes in half horizontally. Whip the cream until just holding its shape. Use the jam and cream to sandwich the cakes together. Serve dusted with icing sugar.