Place 16 mini silicone muffin cases on a baking sheet.
Put the butter, sugar, flour and egg in a bowl and beat with a hand-held electric whisk until light and creamy. Stir in the chopped pecans and divide among the cases.
Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 10–12 minutes, or until risen and just firm. Leave in the cases for 2 minutes, then transfer to a wire rack to cool completely.
Make the maple butter by beating together the butter, vanilla bean paste and icing sugar until smooth and creamy. Gradually blend in the maple syrup, beating well until pale and fluffy. Place in a piping bag fitted with a small star nozzle and pipe swirls on the top of each cake. Decorate with pecan nuts.