Prepare the chicken: On a clean board, season each chicken breast with the smoked paprika, garlic powder, onion powder, salt, and pepper. Dust them lightly with 1 tablespoon of the flour, pressing it in gently. You’ll hear a faint rustle as the flour coats the surface – that’s your cue it’s ready.

Brown the chicken: Heat the butter and olive oil in a large frying pan over a medium-high flame. When the butter stops foaming and smells nutty, place the chicken breasts in the pan in a single layer. Listen for a confident sizzle – if it’s silent, the pan isn’t hot enough. Cook for 4-5 minutes per side, until the underside is a deep, caramelised bronze. The surface should feel firm and look glossy. Transfer the chicken to a plate; it will finish cooking later.

Sweat the aromatics: Reduce the heat to medium. Add the sliced onion to the pan. Stir with a wooden spoon, scraping up the browned bits from the bottom. The onions will release a sweet, earthy aroma as they soften. Cook for 5-6 minutes, until they are translucent and beginning to turn golden at the edges. Add the minced garlic and stir for another minute, until the kitchen smells fragrant and warm.

Build the gravy base: Sprinkle the remaining 2 tablespoons of flour over the onions and garlic. Stir constantly for 1-2 minutes. The mixture will look like a thick, sandy paste. This is the roux – it should smell toasty, not raw. You’ll see it darken slightly to a pale biscuit colour.

Create the creamy sauce: Slowly pour in the chicken stock while whisking vigorously. The liquid will hiss and steam as it hits the hot pan. Keep whisking until the mixture is smooth and begins to thicken, about 2 minutes. The sauce will look glossy and coat the back of a spoon. Stir in the double cream, dried thyme, and mustard powder, if using. The colour will shift to a pale, luxurious ivory.

Simmer the chicken: Return the browned chicken breasts to the pan, nestling them into the sauce. Spoon some of the gravy over the top of each piece. Bring the sauce to a gentle bubble – you want soft, lazy bursts, not a vigorous boil. Reduce the heat to low, cover the pan, and let it simmer for 20-25 minutes. The chicken should feel tender when pierced with a fork, and the gravy will have thickened to a velvety consistency.

Rest and garnish: Remove the pan from the heat. Let the chicken rest in the gravy for 5 minutes. This allows the juices to redistribute. Sprinkle with fresh parsley before serving. The final dish should look glossy, inviting, and deeply comforting.