Pour some water in a pot on the stove to boil and add a bit of salt. When the water starts boiling add the spaghetti to the pot and cook them according to the time indicated in their packet.
Meanwhile, place a frying pan on medium-high heat, add the butter and wait until it is melted, then add the onion and the garlic, both of them well chopped, in order to sauté them.
When the onion turns transparent add the sour cream or milk and mix everything so they integrate well.
Season with the chicken broth powder and keep stirring for a couple more minutes. Then add the shrimp, the salt and pepper as desired, mix and cook everything for 3 more minutes until the shrimp are pink and completely cooked. Set aside this shrimp-based sauce.
When the pasta is ready, drain the hot water and sprinkle some cold water to prevent it from sticking. Drain again and set aside.
Now it is the time to add the rest of the ingredients with the sauce and the pasta. Serve on a plate and mix them well. Sprinkle some grated Parmesan cheese and the parsley as you desire. Serve hot.