Heat oil in large pot over high heat. Add garlic and onion, cook for 1 minute. Then add capsicum and cook until onion is translucent. Add beef and cook, breaking it up as you go. Once the beef turns from red to brown, add remaining ingredients except cheese. Stir, bring to simmer, then turn the heat down to medium. Cover and cook for 10 - 12 minutes or until the macaroni is al dente, meaning just cooked, still a tiny bit on the firm side. Turn the stove OFF but leave the pot on the stove. Stir through half the cheese – it should be a bit saucy. Adjust salt and pepper to taste. Top with remaining cheese, put the lid back on and leave until the cheese melts - about 2 minutes. Sprinkle with coriander, if desired, and serve immediately.