Heat oven to 200C/180C fan/gas 6. Grease a 6-hole muffin tin with butter, then line each hole with a long thin strip of baking parchment. Roll out the pastry on a lightly floured surface and stamp out 6 x 10 cm circles. Press a circle into each hole to line. Roll out the remaining pastry (you may need to re-roll trimmings) and stamp out 6 x 8cm circles.