Turn your oven to 220C and place the chicken carcasses on oven trays and bake until a deep golden colour (should take about 12-18 minutes).

Place a 20-litre pot (or the largest pot you own) on high heat. Place the onions on their flat side in the base of the pot and cook for 15 minutes until blackened. Add the garlic, carrot and olive oil. Stir, cook and colour for two minutes. Add the tomato paste, stirring constantly and cook for a further 3 to 5 minutes. Add the red wine and using a wooden spoon scrape the bottom of the pot making sure that there is nothing sticking to it. Add the chicken bones and the water and bring to the boil. Skim the scum and reduce, cooking for four hours.

Strain the liquid with a strainer to remove the bones and then strain a second time with the finest sieve you have. Place back on the heat and reduce so that there is about 1.5-litres left with a more viscous consistency. Pour into a gravy jug and serve with our barbecued spatchcock.