Pat chicken thighs dry with paper towels and season with salt. Add a drizzle of oil to a large, non-stick frying pan on medium-high heat (choose a pan with a lid as it will be needed later). In two batches, sear chicken for 2-3 minutes on each side until golden (thighs do not need to be cooked through at this point). Set aside on a plate.
Return pan to heat (do not clean; you want to retain the flavours from the chicken), add a drizzle of oil and reduce heat to medium. Add leek rounds and cook for a few minutes on each side until golden. Try to keep the rounds intact as this will prevent them from drying out and they’ll look beautiful for serving.
Mix stock, mustard and honey in a bowl then add to leeks in the pan, along with thyme and seared chicken (plus its juices). Allow to bubble for a minute, then cover with a lid and cook for 8 minutes.
Remove lid and reduce heat to low-medium. Carefully transfer about ¼ cup of cooking liquid to a bowl. Add crème fraîche to bowl, whisk until smooth, then return to the pan. Simmer gently until the sauce thickens slightly. Season generously with freshly ground black pepper. Serve with mashed potato and steamed beans or broccoli.
* Check label if eating gluten free.