Prepare the Meatballs: In a large mixing bowl, combine the chicken mince, breadcrumbs, grated Parmesan, beaten egg, chopped parsley, garlic powder, ½ tsp salt, and ¼ tsp black pepper. Mix gently with your hands until just combined. Be careful not to overmix.

Shape the Meatballs: Lightly wet your hands to prevent sticking, then roll the mixture into about 16 evenly-sized meatballs, roughly the size of a golf ball. For best results, place them on a plate and chill in the fridge for 15 minutes to help them firm up.

Sear the Meatballs: Heat the olive oil in a large, non-stick frying pan or skillet over a medium-high heat. Carefully add the meatballs to the pan, ensuring you don't overcrowd it (work in two batches if necessary). Cook for 5-7 minutes, turning occasionally, until they are golden brown on all sides. They don't need to be cooked through at this stage. Remove the meatballs from the pan with a slotted spoon and set them aside.

Start the Sauce: Reduce the heat to medium. Add the butter to the same pan. Once it’s melted, add the finely chopped onion and cook for 4-5 minutes until soft and translucent. Add the minced garlic and cook for another minute until fragrant.

Cook the Mushrooms: Add the sliced chestnut mushrooms to the pan. Turn the heat up slightly and cook for 6-8 minutes, stirring occasionally, until they have released their liquid and are nicely browned. This browning step is crucial for developing a deep flavour.

Create the Sauce Base: Sprinkle the plain flour over the mushrooms and stir continuously for one minute to cook out the raw flour taste.

Build the Creamy Sauce: Gradually pour in the chicken stock, whisking constantly to avoid lumps. Bring the mixture to a gentle simmer. Add the double cream and the fresh thyme sprigs. Stir well and let it simmer for 2-3 minutes until the sauce begins to thicken slightly.

Finish Cooking the Meatballs: Gently return the seared meatballs to the sauce. Reduce the heat to low, cover the pan, and let everything simmer for 10-12 minutes, or until the meatballs are cooked through and tender. You can check they're cooked by ensuring they reach an internal temperature of 74°C (165°F), as recommended by the Food Standards Agency.

Season and Serve: Remove the thyme sprigs. Taste the sauce and season with salt and pepper as needed. Garnish with extra fresh parsley and serve immediately. I find that letting it sit for five minutes off the heat allows the flavours to settle perfectly.