For the prawns, combine flour, salt, pepper and cayenne pepper in a bowl.
Crack eggs into a bowl and lightly whisk with a fork. Blitz the macadamias in a blender and combine with the breadcrumbs.
To crumb the prawns, dust in the spiced flour, dip in the egg yolk then roll in the macadamia and breadcrumb mix.
Heat oil to approximately 180˚C. To test the oil, drop a piece of bread into the oil – it should go golden brown in about 10 seconds. Once the oil has reached the required temperature, drop about 10 prawns in and cook until they are golden brown. Remove and drain on paper towel. Repeat with remaining prawns.
For the aioli, crush garlic and place in a bowl. Add a pinch of salt and pepper, the egg yolk and mustard and whisk until well combined. Add a few drops of oil, whisking constantly, until the mixture starts to thicken. Slowly pour in the remaining oil in a thin, steady stream, whisking constantly, until combined and the texture is thick and creamy. Add lemon juice in 1 tablespoon at a time until the desired zing is reached.
Serve the macadamia crusted prawns with the aioli as a dipping sauce.
Serving suggestion: Serve with a green salad on the side.