Brown the chicken thighs: Heat the olive oil in a large frying pan over medium-high heat until it shimmers. Add the chicken thighs in a single layer — you should hear a satisfying sizzle. Cook for 3-4 minutes per side until the skin is golden brown and crisp. The chicken should release easily from the pan when it's ready; if it sticks, give it another minute. Transfer to a plate and set aside.

Sauté the aromatics: In the same pan, add the sliced mushrooms and diced onion. Cook for 5-6 minutes, stirring occasionally, until the mushrooms have released their moisture and turned a deep golden colour, and the onions are translucent and fragrant. The kitchen should smell wonderfully earthy and sweet.

Add garlic and tomato paste: Stir in the minced garlic and tomato paste, cooking for 1 minute until the paste darkens to a rich brick-red colour and becomes very aromatic. Be careful not to let the garlic burn — it should smell fragrant, not bitter.

Deglaze the pan: Pour in the white grape juice and chicken broth, scraping the bottom of the pan with a wooden spoon to lift up all the browned bits. This step captures all that concentrated flavour you created earlier. The liquid will look thin and slightly cloudy at this stage.

Layer in the slow cooker: Transfer the mushroom mixture to the crockpot. Nestle the browned chicken thighs into the liquid, making sure they're mostly submerged. Sprinkle over the dried thyme, oregano, salt, and pepper. Give everything a gentle stir to combine.

Slow cook: Cover the crockpot and cook on low for 4 hours or on high for 2 hours. The chicken should be fork-tender and easily pull apart when done. The sauce will look thin and watery at this point — don't worry, we'll thicken it next.

Thicken the sauce: About 15 minutes before serving, whisk the cornflour slurry into the crockpot. Stir well, then replace the lid and cook on high for 10-15 minutes, until the sauce has thickened to a glossy, velvety consistency that coats the back of a spoon.

Finish with butter and rest: Stir in the butter until it melts completely, creating a silky, luxurious finish. Let the dish rest in the crockpot with the lid off for 5 minutes before serving. This allows the flavours to meld and the sauce to settle beautifully.

Garnish and serve: Sprinkle with fresh chopped parsley just before serving. The bright green flecks against the rich, golden sauce make for a stunning presentation.