<p>1. preheat the oven to 375&deg;F/190&deg;C</p>
<p>2. Place poussin, breast-side down, with the tail towards you.&nbsp; Using sturdy scissors or poultry shears, cut up along each side of the backbone to remove it, cutting through the rib bones as you go.&nbsp; Open the chicken out and turn over. Flatten the breastbone with the heel of your hand so that the meat is all one thickness.</p>
<p>3. Place spatchcock chicken into a roasting tin and season with salt and the crushed mixed peppercorns then drizzle with olive oil.&nbsp; Place into the oven for 45 minutes.</p>
<p>4. When the chicken has 20 minutes to go, put the potatoes into a steamer for 20 minutes.</p>
<p>5. After 5 minutes steam the leeks for 10 minutes.</p>
<p>6. Whilst the leeks are steaming, gently fry the onions and garlic for about 5 minutes in a little olive oil.&nbsp; Finely chop 25g of the oyster mushrooms, add to onions and garlic and fry for a further 5 minutes. by this stage your chicken is hopefully cooked.</p>
<p>7. In a pan melt a large knob of butter on a medium to high heat, remove the leeks from the steamer and add to the pan with some salt and a good amount of black pepper. Keep an eye on these you want to sautee them for about 5 minutes.</p>
<p>8. Roughly tear the remaining 50g of oyster mushrooms and add to the onion mix.</p>
<p>9. Remove the chicken from the oven and place on a plate to rest.&nbsp; Add the water to the roasting tin to pick up all the lovely flavour end pour into the onions.&nbsp; Turn the heat right up to reduce the liquid down.</p>
<p>10. Once the liquid has mostly gone, turn the heat down and add the creme fraiche, allow to heat through.</p>