Trim the mushroom stalks level with the caps, then chop the stalks finely and reserve.

Roll out the pastry thinly on a lightly floured surface. Then, using a 7.5 cm (3 inch) fluted round cutter, cut out 24 pastry rounds.

Place one mushroom, stalk side up, on each of 12 pastry circles. Put a small knob of butter, a pinch of marjoram and a sprinkling of pepper on each mushroom.

Brush the edges of each mushroom-topped pastry circle with beaten egg, then place a second circle of pastry on top. Bring together the pastry edges, pressing well to seal. Flute the edges.

Dampen 2 baking sheets and transfer the puffs to them. Cover the puffs with cling film and refrigerate for 15 minutes.

Heat the oven to 220C/425F/Gas 7.

Meanwhile, make the Stilton sauce: crumble the cheese into a serving bowl, add a little yoghurt and mix together with a fork until fairly smooth. Stir in the remaining yoghurt, reserved mushroom stalks and half the spring onions. Sprinkle the remaining spring onions on top of the sauce, cover with cling film and refrigerate.

Brush the tops of the puffs with the remaining beaten egg, then bake in the oven for 10 - 15 minutes until well-risen and golden brown.

Pile the hot puffs on to a warm serving plate and serve with the chilled sauce handed separately (see Serving ideas).