Preheat the oven to 220°C (200°C fan oven) gas mark 7. Heat the sunflower oil in a large saucepan over a high heat and add the chicken legs, skin side down, along with the wings and the carcass (you may need to do this in batches, depending on the size of your pan). Fry over a very high heat, to brown all over. Transfer to a roasting tin and coat in a little more oil and a pinch of salt. Roast for 15–18 minutes until a deep golden brown.
Add the vegetables to the same pan (there should still be some oil in there) and put it back over a medium heat. Sweat the veg for two minutes or until starting to soften but not colour.
Once roasted, return the chicken to the pan and pour over two litres cold water. Season with salt and pepper. Bring to the boil, then reduce the heat and simmer for one and a half hours. Strain the soup and return the broth to the pan. Take the chicken from the sieve, remove the skin and shred the meat from the bones, discarding the bones and skin. Leave the meat to one side.
Divide the wild garlic among serving bowls and top with the spring onions. Divide the shredded chicken between the bowls and add the herbs.
Taste the broth and check for seasoning, adding more salt and pepper if needed. Ladle it over the chicken and greens in the bowl, and sprinkle over the garlic flowers, if you have them.