I love the small baby chickens that producers label spring chickens, poussins or coquelettes. The size – about 500g each (17¾oz) – is plenty for one person, and the meat is tender and moist. They’re more expensive than fully grown chickens, so I reserve them for dinner parties.
Start marinating the birds on the morning of the day you're going to cook them. Because they're so small, the chickens take only about 30 minutes to cook (assuming they are 500g; adjust the time if the birds are larger). Try to buy birds that are about the same weight. You can cook them in the oven, using the grill setting (with convection, if your oven has this option), or outside on the barbecue.
I learned to make nam jim jaew from a friend who was from Isaan, Thailand. The sauce is addictive, and I sometimes make a double batch so I have a supply in the fridge, ready to perk up other types of grilled meat.
Khao khua is glutinous rice that's been toasted, then ground to a grainy powder. It's also called roasted (or toasted) rice powder. If you can't find it in the Thai shops, make your own.
Split open and partially debone the chickens. Place a bird, breast side-down, on a cutting board, with the tail facing you. Use kitchen shears to cut the bird along one side of the backbone, cutting from the tail to the neck. Turn the bird around then cut along the other side of the backbone, this time cutting from the neck to the tail. Open up the chicken and place it skin-side up on the cutting board. Press the bird firmly with your hand until you hear the bones crack, then flip it over. Run your fingers under the rib bones and shoulder bones to detach them from the meat. Pull out the rib bones (if needed, use kitchen shears to cut them from the breastbone). Snap off the shoulder bones from the carcass. When you're finished, the chicken will have the leg and wing bones, and the breastbone and wishbone. Do the same to the remaining birds then put them in a large bowl.
Make the marinade. Finely chop the garlic, chillies and fresh coriander roots, and thinly slice the lemongrass. Put these ingredients and the palm sugar in the bowl of the chopper attachment of an immersion blender (or a small food processor) and process to a rough purée (or you can pound the ingredients in a mortar). Mix in the fish sauce, lime juice and white pepper, then pour the marinade over the birds in the bowl and mix well. Cover the bowl and refrigerate for at least four hours (eight is better), mixing occasionally.
Make the nam jim jaew. If the palm sugar is too hard, microwave it briefly until it’s soft. Mix the palm sugar with the fish sauce, lime juice, glutinous rice powder and chilli powder. Halve the shallots then thinly slice them. Cut the spring onions into thin rounds, and roughly chop the coriander. Add the ingredients to the fish sauce mixture and stir.
Let the chickens come to room temperature before grilling them. If cooking the chickens in the oven, turn the grill function (with convection setting, if possible) to high.
Take the chickens from the marinade and place them skin side-up on a grill rack placed over the grill tray. Brush some of the marinade over the skin, and spoon some of the marinade’s solid ingredients on top. Put the birds about 5cm (2in) away from the grill element at the top of the oven.
Cook for about 30 minutes (for 500g birds), turning the tray around halfway through; if the skin gets too dark, move the tray further away from the heat. The chickens should be well-bronzed and slightly charred in spots. Cook the chickens until an instant-read thermometer inserted into the thigh (but not touching the bone) reaches 70°C (160°F). Remove the tray from the oven and let the birds rest for 10 minutes, after which the internal temperature should reach 75°C (170°F).
If you’re grilling the birds on the barbecue, prepare the coals about 45 minutes before you want to cook the meal. When the coals are white and glowing, spread them evenly over the bottom of the barbecue. Place the birds skin side-down on the grill rack placed about 8cm (3⅜in) away from the coals. Cover the barbecue with the lid and cook until the internal temperature reaches 70°C (160°F). Watch the chickens carefully and if they get too dark, move the grill rack further away from the heat; if they’re too pale, move them closer to the coals. Turn them over halfway through. When the internal temperature reaches 70°C (160°F), take the chickens from the barbecue and place them skin side-up on a cutting board to rest for 10 minutes.
You can serve the birds whole, halved or quartered. Serve with steamed Thai sticky rice, with the bowl of nam jim jaew on the side.