Heat two tablespoons of the oil in a heavy-based saucepan and fry the onions for 5-10 minutes, or until golden-brown.
Mix the onion, chili, garlic and haggis in a bowl until well combined. Place the flour into a separate bowl whisk in 125ml/4fl oz warm water until the consistency of double cream.
Stir the onion mixture into the batter until well combined. Using two teaspoons, shape the mixture into small quenelles.
Fill a deep-fat fryer or a large, deep, heavy-bottomed pan two-thirds full with vegetable oil. Heat the oil to 180C/350F (use a probe thermometer to check the temperature if you're not using a deep-fat fryer). (CAUTION: Hot oil can be dangerous. Don't leave unattended)
Carefully place the bhajis in the hot oil and cook for 2-3 minutes or until just cooked through. Remove from the oil using a slotted spoon and drain on kitchen paper. (This may need to be done in batches.)
For the dip, place all of the ingredients into a saucepan and boil until the ingredients until thickened slightly.