Place puff pastry slices next to each other on the work surface and allow to defrost. Peel, wash and slice the carrots. Clean and trim the mushrooms and cut them into quarters. Peel onion and cut into cubes. Wash the meat, dab dry and cut into cubes.
Heat oil, fry meat for about 10 minutes, turning. After 5 minutes, add onion, carrots and mushrooms and fry. Season with salt and pepper. Add cream and stock, bring to the boil and simmer for about 5 minutes. Pour ragout into 4 oven-proof cups (approx. 250 ml content). Place the puff pastry on the cups, press down on the rim and cut off protruding corners. Place the pastry remnants on top of each other, roll out on the floured worktop and cut out 4 circles with a cookie cutter and place them on the pastry covers. Whisk egg yolk and milk and spread the dough covers. Bake in the preheated oven (electric range: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 10 minutes.
Pour ragout into 4 oven-proof cups (approx. 250 ml content). Place the puff pastry on the cups, press down on the rim and cut off protruding corners. Place the pastry remnants on top of each other, roll out on the floured worktop and cut out 4 circles with a cookie cutter and place them on the pastry covers. Whisk egg yolk and milk and spread the dough covers. Bake in the preheated oven (electric range: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 10 minutes. Wash the chervil, shake dry, pluck the leaves from the stems and sprinkle over the pie.