Put water in a saucepan and boil it. Then add the spaghetti and cook them for 8-10 minutes. Once the spaghetti has boiled, heat the olive oil in a frying pan, put the chicken in it and cook it for about 4 minutes on each side of until it turns brown. Place the chicken on a plate and add olive oil and butter into the pan along with garlic, onion and the cream. Last but not least, add some salt and pepper, for extremely intense flavors. Mix the ingredients well. Then, lower the heat and put the chicken back in the pan and wait for the sauce to thicken.