In a large saucepan brown bacon until crispy and discard excess grease. Add onions and cook for a few minutes until wilted.
Combine soy sauce, garlic, tomato puree, golden syrup, molasses, brown sugar and optional liquid smoke. Add to bacon and onion in the saucepan. Season with chilli powder, mustard, paprika, cayenne, ground cloves, bay leaf and salt. Bring to a boil, reduce heat and simmer for 45 minutes to 1 hour.