Steam broccoli, cauliflower and romanesco in steamer baskets or on the sieve insert until just tender. Steam the peppers for the last 2 to 3 min. Melt butter, add flour and mushrooms and steam until soft, stirring continuously with a whisk.
Extinguish with soup and milk, let it boil up while stirring continuously. Season with salt and pepper, gently simmer at low temperature for 10 to 15 min.
Bake puff pastry patties in oven heated to 200 °C for approx. 5 min. Divide patties evenly on plates. Fill the vegetables into the patties and pour the sauce over them.