Using an electric mixer, beat the butter and sugar together until light and creamy. Gradually beat in the eggs one at a time until well combined. Mix the espresso powder or coffee granules with the boiling water to form a syrup. Add the coffee syrup and vanilla extract to the butter and sugar mixture and beat until smooth.

Sift in the flour, then mix gently with a spoon until well combined. Form the dough into a flattened disc, wrap it in clingfilm and chill in the refrigerator for at least an hour until firm.

Preheat the oven to 180°C/350°F/Gas Mark 4. Line 2 baking sheets with baking paper. Allow the dough to soften slightly at room temperature. Roll small ovals of the biscuit dough about 1 cm (½ inch) long and place them on the lined baking sheets. Press a cocktail stick horizontally along each biscuit to imprint a line down the centre to form the coffee bean shape. Bake the biscuits in the preheated oven for 3–5 minutes until just firm to the touch. Allow them to cool completely on a wire rack.