Preheat your oven to 200°C/Fan 180°C/Gas 6. Unwrap the chicken and remove the giblets – you can use them for homemade stock (see our tip).
Pop the chicken into a roasting tin. Halve the garlic bulb and insert it into the chicken’s cavity. Rub the chicken with ½ tbsp Thai curry paste (save the rest for later) and set the chicken aside for 30 mins to come to room temperature. When you’re ready to cook the chicken, cover it with foil, crimping it to the sides of the tin to seal. Slide the chicken into the oven to roast for 1 hr.
Remove the chicken from the oven and turn the temperature up to 220°C/Fan 200°C/Gas 7. Remove the foil. Baste the chicken with any pan juices and season it with a big pinch of salt.
Pop the chicken back in the oven, without the foil, and roast for 30 mins, or till the skin is golden and the chicken is cooked through. You can check if it’s done by inserting a skewer into the thickest part of a thigh. If the juices run clear, it’s ready. If not, slide it back into the oven for another 15 mins.
When it’s done, lift the roast chicken out onto a plate or board and carefully remove the garlic bulb. Loosely cover the chicken with foil and set it aside to rest for 30 mins.
While the chicken rests, squeeze 3-4 cloves from the roast garlic bulb and mash them with the back of a knife (see our tip for the remaining roast garlic). Peel and finely grate the ginger.
When you’re nearly ready to serve, make the coconut sauce. Pour any roasting tin juices into a small pan and add the remaining ½ tbsp Thai red curry paste, 1 tbsp fischy sauce, the ginger and mashed garlic. Pour in the coconut milk. Simmer for a few mins to warm through.
Carve the chicken and serve with the red Thai coconut sauce on the side.