Spaghetti Bolognaise

I think most of my friends know how to make this, but recently, some friends asked me for the recipe. I don't have a recipe and it turns out different every time, but my Dad taught me how to make it when I was 10 and it is one of the easiest things for me to make. I always make this when there is nothing in the fridge and I don't feel like cooking.
Ingredients:
Olive oil
1 onion, chopped
2 cloves garlic, minced
1 green pepper, chopped
1 red pepper, chopped
500 g mince
1/2 cup button mushrooms, or shimeji
Other vegetables I sometimes add: 1/2 cup corn or 1/2 bunch spinach
1 can diced tomatoes
1/2 cup tomato puree
2 tbsp tomato paste
1 tbsp dried or fresh basil
1 tsp oregano
salt and pepper
300g spaghetti
Parmesan cheese
Fry onion and garlic in olive oil for 2 or 3 mins. Add mince and brown. (Adding 1/2 cup of red wine at this point makes it richer, but I never have any!) Add red and green pepper, mushrooms and other vegetables to the pan. Once liquid had dried up add can of tomatoes, puree, basil, oregano, salt and pepper. Wash can of tomatoes out with a little water and add to pan. Bring to the boil, then simmer for at least 20 minutes.
In a pot boil spaghetti with lots of water and a little salt, until desired softness.
Drain spaghetti and put bolognaise sauce on top. Sprinkle with Parmesan cheese.