Prepare the Chicken: Place each chicken breast between two sheets of cling film. Using a meat mallet or a rolling pin, gently pound the chicken to an even 1.5 cm thickness. This ensures even cooking. Season both sides generously with salt and freshly ground black pepper. Dredge each piece lightly in plain flour, shaking off any excess. The chicken should feel lightly coated, not caked.

Sear the Chicken: Heat 30ml olive oil in a large, heavy-bottomed frying pan or skillet over medium-high heat until shimmering. Carefully place the floured chicken breasts into the hot pan, ensuring not to overcrowd it (cook in batches if necessary). Sear for 3-4 minutes per side, until the chicken is beautifully golden brown and has a lovely caramelised crust. It doesn't need to be cooked through at this stage; we're building flavour. Remove the chicken from the pan and set aside on a plate. The kitchen will start to smell wonderfully savoury from the searing chicken.

Sauté Aromatics and Mushrooms: Reduce the heat to medium. Add the unsalted butter to the same pan. Once melted, add the sliced button mushrooms. Sauté for 5-7 minutes, stirring occasionally, until they release their moisture and turn a deep, golden-brown colour, becoming tender. You'll hear a gentle sizzling sound and notice their earthy aroma intensifying. Add the finely chopped shallot and minced garlic, cooking for another 1-2 minutes until fragrant and softened, taking care not to burn the garlic. The shallots should look translucent.

Build the Sauce: Pour in the beef stock, chicken stock, Madeira-style cooking sauce, and balsamic vinegar. Add the dried thyme. Bring the mixture to a gentle simmer, scraping up any browned bits from the bottom of the pan with a wooden spoon – these bits are packed with flavour! Let the sauce simmer for 5-8 minutes, allowing it to reduce slightly and thicken, until it coats the back of a spoon. The aroma will become wonderfully rich and complex.

Finish the Sauce and Chicken: Reduce the heat to low. Stir in the double cream until fully incorporated. The sauce should turn a lighter, creamy brown colour and look velvety smooth. Return the seared chicken breasts to the pan, nestling them into the sauce. Cover the pan and let the chicken gently poach in the sauce for another 8-10 minutes, or until cooked through and tender. To check for doneness, the internal temperature of the thickest part of the chicken should reach 74°C (165°F). The chicken will feel firm to the touch.

Serve: Taste the sauce and adjust seasoning with salt and freshly ground black pepper if needed. Garnish generously with fresh chopped parsley before serving immediately. The vibrant green of the parsley will contrast beautifully with the rich brown sauce.