Cook spaghetti in large pot of boiling salted water until just tender but still firm to bite, stirring occasionally. Drain, reserving 1/2 cup spaghetti cooking liquid. Return it to pot.
Meanwhile, add chopped onion, garlic, tomatoes, capsicum into the heated olive oil and sauté well. Either chicken can be kept separately as fried pieces with it or it can be chopped into cube shapes and added along with the above items. In the latter case add the chicken pieces and chicken stock [mixed well in light hot water (1/2 glass)]. Season it with salt and pepper. Sauté the entire ingredients well. Add fresh cream.
Pour this mixture/fresh cream sauté over the spaghetti and toss to coat, adding spaghetti cooking liquid by tablespoons if dry. Transfer to bowl. Serve passing additional parmesan alongside.