Preheat oven to 180C. Scatter mushroom slices on a baking tray along with crushed garlic, oregano, salt and pepper. Drizzle generously with olive oil and combine well. Cook for approximately 30 minutes or until mushrooms are dark and crispy (keep your eye on them whilst cooking and be careful not to burn or blacken). Remove from oven when ready and set aside.
In a medium saucepan fry onions in olive oil until soft. Add garlic, oregano, dried chilli, carrot and celery and continue to cook on a low heat until soft.
Next, add tomato paste, stir through and cook until dark and sticky.
Cooking the tomato paste this way adds the foundation of flavour to the rest of the tomato sauce, giving it a rich depth.
When this is done add the red wine, bring to the boil, then turn to simmer until reduced by half.
Chop halloumi into chunks then blend with oil and water until smooth.
Returning to the saucepan, add tinned tomatoes and vinegar-sugar mix. Fill the empty tomato can 1/3 way with water, swirl around to collect leftover tomato and add this to the sauce. Next stir blended halloumi in with the tomato sauce until completely combined. Bring to the boil, turn to simmer, stir sauce again to loosen, then cover with a lid and gently simmer for 15 minutes.
Meanwhile, using your hands crush roasted mushroom bits into small pieces so it resembles mince. Add mushroom mince to tomato sauce, stir through, cover again and continue to simmer for another 5 minutes.
Cook spaghetti to packet instructions.
Mix bolognese sauce and spaghetti together and divide between bowls. Garnish with parmesan cheese and fresh basil leaves.