Defrost the puff pastry briefly on the floured work surface. Roll out onto the double, cut out approx. 50 flowers with a flower-shaped biscuit cutter and place on a baking tray lined with baking paper.
Whisk 1 egg yolk and 2 tablespoons of milk and spread a thin layer of puff pastry. Bake in the preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: see manufacturer) for approx. 7 minutes.
Clean the mushrooms and halve or quarter them depending on size. Peel onions and cut into cubes. Wash the meat, dab dry and cut into short strips. Heat the fat and fry the meat for approx. 5 minutes, turning it over.
After about 3 minutes add onions. Season with salt and pepper.
Dust with flour. Add stock and milk while stirring. Bring to the boil and simmer for about 15 minutes. Add mushrooms and peas and cook briefly in the soup. Season to taste with lemon, salt and pepper.
Whisk the remaining egg yolks and cream. Remove the pot from the heat and stir the mixed egg yolks into the soup. Soup must not boil up any more.