Photograph: Laura Edwards
Mix the fish sauce, sugar and lime juice, pour over the chicken and marinate for 15 minutes. Preheat the oven to 200°C, fan 180°C, gas 6.
Chop the breadcrumbs, kaffir lime leaves, garlic, ginger, onions and salt together until a little finer. Transfer to a bowl; mix in 1 tablespoon of the oil.
Transfer the chicken to a roasting tin (discard the marinade); toss in the remaining oil. Firmly press the crumb mixture on top of each breast, drizzle over a little extra oil, season with black pepper and roast for 25 minutes.
Put the oils in a jug. In a bowl, whisk the yolk and salt, then add half the oil, drop by drop. Whisking, slowly add 1 tablespoon lime juice, the zest and remaining oil until thick. Grate the ginger; squeeze to get ½ teaspoon of its juice – add to the mayonnaise; chill. Serve with the chicken and wedges.
Get ahead: make the crumb topping (don't add the oil) and the mayonnaise a day ahead; store both in the fridge.