Peel and wash the spinach in several waters, drain them, cook them without water in a large covered saucepan. Salt and pepper at the end of cooking, drain, set aside.
Peel and cut the carrots into sticks, cook them in boiling salted water for 5 minutes, cool, set aside.
Put the raspberry vinegar in a sauté pan, let it reduce until you obtain a teaspoon of liquid, moisten with the chicken stock, let reduce by half, add the cream, salt and give two turns of the pepper mill , cook for 2 minutes.
Glaze the rectangles of puff pastry using a brush dipped in beaten egg and bake in the oven. 6 (200°C) 15 minutes.
Open the puff pastries, garnish them with the spinach and carrots, then coat each puff pastry with the sauce. Garnish with chopped chives.
You can replace spinach and carrots with cauliflower and broccoli, it's delicious.
