Sear the Chicken: Pat the chicken pieces dry with a paper towel and season generously with salt and pepper. Heat the olive oil and butter in a large, heavy-based frying pan or skillet over a medium-high heat. Once the butter is foaming, add the chicken in a single layer. What works best for me is searing it in two batches to avoid overcrowding the pan. Cook for 3-4 minutes per side, until deeply golden brown. The chicken doesn't need to be cooked through at this stage. Remove it from the pan and set aside on a plate.

Sauté the Aromatics: Reduce the heat to medium. Add the chopped onion to the same pan and cook for 5-6 minutes, stirring occasionally, until softened and translucent. Add the minced garlic and cook for another minute until fragrant.

Cook the Mushrooms: Add the sliced mushrooms to the pan. Increase the heat slightly and cook for 6-8 minutes, stirring infrequently at first to allow them to brown properly. They will release some water, which should evaporate as they continue to cook and turn a lovely golden colour.

Deglaze the Pan: If using, pour in the white wine. Use a wooden spoon to scrape up any browned bits from the bottom of the pan – this is called fond, and it's packed with flavour. Let the wine bubble away and reduce by about half, which should take 2-3 minutes.

Create the Sauce: Pour in the chicken stock, add the fresh thyme sprigs, and bring to a simmer. Let it bubble gently for 5 minutes to reduce and intensify the flavour.

Make it Creamy: Reduce the heat to low and stir in the double cream. Let the sauce warm through gently, but avoid boiling it. Taste the sauce now and season with salt and pepper as needed.

Finish the Dish: Return the seared chicken and any juices from the plate back into the pan. Stir everything together and let it simmer gently for another 5-7 minutes, or until the chicken is cooked through and the sauce has thickened slightly. Remove the thyme sprigs before serving.

Garnish and Serve: Sprinkle with freshly chopped parsley and serve immediately.