Wash and peel the asparagus and cut it diagonally into bite-sized pieces. Boil the asparagus shells in 3/4 litres of salted water, cover and cook for about 5 minutes. In the meantime clean and wash the mangetouts.
Lift the asparagus shells out of the water with a skimmer. Add the vegetables to the water, cover and cook for 8-10 minutes. Pour the vegetables onto a sieve and collect the vegetable water. Place puff pastry sheets next to each other and defrost.
Peel and chop the onion. Wash the chicken filet, dab dry and cut into cubes. Heat clarified butter in a pan and fry the chicken cubes all around. Add onions, braise briefly and season with salt and pepper.
Deglaze with white wine, 1/2 litre vegetable water and cream, except for a teaspoon. Bring to the boil, add sauce thickener while stirring and cook for another 1-2 minutes. Add vegetables to the ragout and season with salt and pepper.
Pour into a casserole dish. Place puff pastry sheets on top of each other and roll out 4-5 cm larger than the diameter of the form. Separate the egg. Brush the edges of the mould with egg white and place the pastry lid on top.
Cut off the excess dough to about 2 cm. Mix the egg yolk and the rest of the cream and brush the lid with it. Then cut in from the edge with a knife, leaving a middle piece of 5-6 cm Ø.
Bake in the preheated oven (electric: 225 °C / gas: level 4) for 10-15 minutes. Cut out figures from the leftover dough as you like, bake them separately and decorate or add to the finished pie.
Serve with rice if desired.