Brown the Chicken: Pat the chicken thighs dry with kitchen paper. Heat 2 tablespoons of olive oil in a large frying pan over a medium-high heat. Place the chicken skin-side down in a single layer; you'll hear a satisfying sizzle. Cook for 3-4 minutes until the skin is a deep golden brown and releases easily from the pan. Flip and cook for another 2 minutes. The smell of seared poultry will fill your kitchen. Transfer the chicken to a plate; you won't cook it through here, just colour it.

Sauté the Vegetables: In the same pan, add the remaining tablespoon of olive oil. Tip in the sliced onions and bell peppers. Cook for 5-6 minutes, stirring occasionally, until they soften and the onions turn translucent. The edges of the peppers should begin to char slightly. Add the minced garlic and cook for 30 seconds until fragrant—don't let it burn.

Deglaze the Pan: Pour in a splash of the chicken stock and scrape up any browned bits stuck to the bottom of the pan with a wooden spoon. This step unlocks all the savoury flavour from the seared chicken. Let it bubble for a minute until it reduces slightly.

Build the Sauce Base: Transfer the cooked vegetables to the slow cooker. Add the tinned chopped tomatoes, tomato purée, remaining chicken stock, dried oregano, dried basil, and the bay leaf. Stir everything together until well combined. The mixture should look a vibrant, rich red.

Add the Chicken: Nestle the browned chicken thighs into the sauce, skin-side up, so they sit partly submerged. Pour any juices from the plate into the slow cooker too. Season generously with salt and pepper.

Slow Cook: Place the lid on and cook on low for 6-7 hours, or on high for 4 hours. After 3 hours on high, the sauce will be bubbling gently and the kitchen will smell wonderfully aromatic. The chicken is ready when it is fork-tender and pulls apart with no resistance.

Finish and Serve: Carefully remove the bay leaf and discard. Using tongs, lift the chicken out onto a serving platter. If you prefer a thicker sauce, switch the slow cooker to high and let it simmer uncovered for 10-15 minutes, until it reduces slightly. Taste and adjust the seasoning. Spoon the sauce over the chicken and garnish with fresh parsley.