For the parsley puree: Place garlic in a small saucepan, cover with cold water and bring to the boil. Drain and repeat this twice more. Slip garlic out of its skin and replace in the small pot, this time with the cream. Add one-third of the picked parsley leaves, cover and simmer very gently for 10 minutes.

Meanwhile bring a larger pot of lightly salted water to the boil. Plunge in the rest of the parsley leaves for half a minute. Drain and run under the cold tap immediately. Squeeze dry (not too vigorously) with a clean cloth and immediately transfer the cream/garlic/parsley mixture and the drained parsley to a blender and turn it on. Let it run for quite some time until you have a brilliant green puree. Scrape into a small bowl and reserve in a warm spot.

For the pastry: Preheat oven to 200C. Place puff rectangles on a baking sheet. With a sharp knife and a steady hand cut a border 1cm in from the edges, not cutting through to the bottom. Whisk egg yolk with a fork and brush just the border you have made. Bake for 10 minutes. Lower heat to 170C and bake for 15 minutes. Remove pastries (they will resemble shallow vol-au-vents), cool a little and with a sharp knife gently separate the "lids" that will have formed. Set pastries aside.

For the mushrooms: If using buttons, cut into quarters. If using small flats, trim stalks flat.

Heat butter in a frying pan and toss the mushrooms in the butter. When glistening, season lightly, add the water and the stock, and cover the pan and cook over moderate heat for five minutes. Remove cover, if there is a lot of liquid raise the heat. Scatter over the sliced truffle and watch carefully. You want a moist sticky mixture, not scorched but not sloppy.

To assemble: Warm pastries briefly in the oven. Spoon in the parsley puree, then pile in the mushroom truffle mixture and lightly settle the lids on top or at a rakish angle.

Makes 2

*The Careme brand is superior to anything on the market. I would never make my own puff ever again.