Method

• 1.
  Preheat oven to 200°C/180°C fan-forced.
• 2.
  For the aioli, wrap the garlic bulb in foil and roast for 40-45 minutes, until garlic is tender. Unwrap garlic and set aside until cool enough to handle.
• 3.
  Squeeze out garlic cloves into a food processor, discarding skins. Add egg, egg yolk, juice and mustard. Whiz until smooth. Combine olive and grapeseed oils in a jug and, with motor running, gradually add to garlic mixture until smooth and combined. Season and transfer aioli to a serving bowl.
• 4.
  Meanwhile, place onion in a large bowl with enough iced water to cover and stand until ready to cook (see notes).
• 5.
  Place flour in a shallow bowl, whisk egg and milk in a second shallow bowl and place seasoned breadcrumbs in a third shallow bowl. Dust onion with flour, shake off excess, then dip in egg mixture and coat in breadcrumbs. Place on a plate and refrigerate for 20 minutes.
• 6.
  Half-fill a deep-fryer or large saucepan with vegetable oil and heat to 180°C (a cube of bread will turn golden in 60 seconds when the oil is hot enough). In batches, deep-fry onion rings, turning occasionally, for 2-3 minutes, until golden and crisp. Remove with a slotted spoon and drain on paper towel. Season to taste.
• 7.
  Transfer onion rings to a serving platter. Serve with aioli on the side