Wash, dry and cut into strips the pepper, finely cut the onion too.
Put the water to boil for the pasta and salt it.
In an anti-adherent frying pan, of such a size as to be able to pour the pasta and then whisk it with the ingredients, let the onion simmer with a little water; after a few minutes add the extra virgin olive oil and the peppers cut into strips. Stir and let go for a few minutes on medium heat.
After this time join the refugees (in my case they are already cooked but, if you use fresh mushrooms, add them when you put the peppers).
Lower the heat, add salt, stir, add the milk and a cup of water and cook until the sauce becomes creamy (it will not take long). Do not forget to mix from time to time.
Cook the pasta al dente, drain it - leaving a little 'cooking water - and pour into the pan with the sauce.
Cook over high heat for a couple of minutes, mixing all the ingredients carefully.
At this point you just have to serve and serve the bucatini with peppers and mushrooms still steaming and fragrant!
Source: http://blog.giallozafferano.it/ilbellodelfornello/?p=2954