Boil spaghetti in sufficient quantity of salted water till al dente. Drain, apply oil and keep aside. Marinate chicken pieces in Worcestershire sauce. Heat equal quantities of olive oil in two separate pans. Add garlic to both the pans and sauté. Add marinated chicken to one pan and sauté for five minutes.
Add tomato puree and tomato ketchup and mix. Add the three coloured capsicums, salt and pepper powder. Add basil leaves torn with hands. Remove when chicken is done. Add onion to the other pan and sauté. Add button mushrooms and continue to sauté for two to three minutes. Add spinach, fresh cream, salt and pepper powder and mix.
Remove and keep aside. Preheat oven to 200°C. Take a baking dish and spread half of the white sauce at the base. Over this spread half of the spaghetti and cover with the spinach and mushroom mixture. Spread half of the processed cheese and cover with remaining spaghetti and white sauce. Spread chicken mixture and cover with remaining processed cheese. Bake in the preheated oven at 200°C for fifteen minutes. Serve hot.