Clean and clean the mushrooms and cut them into small cubes. Peel garlic and chop finely. Wash parsley, dab dry, remove leaves and cut into strips. Heat 2 tablespoons of oil in a frying pan. Fry the mushrooms for about 5 minutes. Add garlic and 2/3 of the parsley. Season with salt and pepper and continue to fry for about 2 minutes. Remove mushrooms from the pan
Take the puff pastry out of the fridge about 10 minutes before processing. Wash the meat and pat dry. Cut a pocket into each chicken filet horizontally on the long side. Fill pockets with mushrooms. Season with salt and pepper
Unroll the puff pastry and roll it slightly thinner on a floured work surface. Cut the dough into 4 rectangles (each approx. 13 x 23 cm). Wrap poultry breasts in it. Place the puff pastry pockets with the pastry seam facing downwards on a baking tray lined with baking paper
Whisk the egg yolk with 1 tbsp. water and brush the pockets with it. Bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for 25-30 minutes until golden brown
Peel the shallots and cut into thin rings. Heat 1 tablespoon of oil in a frying pan. Sauté the shallots in it for about 3 minutes, then deglaze with wine. Let the wine boil down about halfway. Add mustard and whipped cream and simmer for another 3-4 minutes. Season the sauce with salt, pepper and possibly some sugar
Wash the tomatoes. Heat olive oil in a pan. Fry the tomatoes for 5-7 minutes. Season with salt and pepper. Arrange the puff pastry pockets, tomatoes and sauce on plates and sprinkle with the remaining parsley