With lettuce standing in for a bun (or bau) in this hand-held Chinese classic, san choy bau is a carb-free favourite. But the lettuce here is more than just a way to ferry flavour to your mouth, it also adds a crisp freshness that balances the richly satisfying pork and sweet eggplant.
Cut eggplant into 2cm pieces. Peel and thinly slice garlic. Thinly slice spring onions, keeping the white and green parts separate. Drain water chestnuts and finely chop. Carefully separate lettuce leaves and finely chop the inner core.
Place hoisin sauce and soy sauce in a bowl and mix to combine.
Heat 1/2 the vegetable oil in a wok or large frypan over medium-high heat. Add eggplant, salt and pepper, and cook, stirring, for 8 minutes or until golden brown and softened. Remove from pan and set aside.
Wipe out frypan or wok and add remaining oil and pork mince. Cook, breaking up lumps with a wooden spoon, for 5-6 minutes or until mince is golden. Add sesame oil, garlic and white spring onion, seasoning with salt and pepper, and cook for 1 minute or until aromatic.
Add water chestnuts, lettuce core and sauce mixture and cook for a further 2 minutes or until warmed through and pork is coated in sauce.
Gently fold eggplant through pork to warm through, and season to taste with salt and pepper. Spoon into lettuce cups. Scatter with green spring onion to serve.