Season and sear the chicken: Pat the chicken thighs dry with kitchen paper, then season generously with salt, pepper, and the smoked paprika. Heat the olive oil in a large frying pan or skillet over a medium-high heat. When the oil shimmers and you see a faint wisp of smoke, place the chicken thighs in a single layer. Let them cook undisturbed for 4–5 minutes, until the underside turns a deep golden brown and releases easily from the pan. Flip each piece and cook for another 3 minutes. The surface should feel firm to the touch, and the kitchen will smell smoky and savoury. Transfer the chicken to a plate and set aside.

Sweat the aromatics: Reduce the heat to medium. Add the chopped onion to the pan, scraping up any browned bits from the bottom with a wooden spoon. Cook for 3–4 minutes, stirring occasionally, until the onion becomes translucent and softens — you'll notice it turns from white to a pale, glassy yellow and releases a sweet, mellow aroma. Stir in the minced garlic and dried oregano, and cook for another 30 seconds until the garlic becomes fragrant but not coloured.

Toast the orzo: Pour the uncooked orzo into the pan and stir it through the onion mixture. Let it toast for 1–2 minutes, stirring constantly. The orzo grains will change from a pale cream colour to a light golden tan, and you'll hear a faint crackling sound as they begin to toast. This step adds a nutty depth to the final dish.

Add the liquid: Pour in the hot chicken stock, the lemon juice, and half of the lemon zest. Stir everything together, scraping the bottom of the pan to release any stuck-on flavour. The liquid will bubble vigorously at first, then settle into a gentle simmer. The stock should look clear and glossy, flecked with tiny bits of oregano and lemon zest.

Return the chicken and simmer: Nestle the seared chicken thighs back into the pan, pushing them gently into the orzo mixture. Bring the liquid to a steady simmer — you should see small, lazy bubbles breaking the surface. Cover the pan with a lid, reduce the heat to low, and let it cook for 15 minutes. After 15 minutes, remove the lid and check the orzo: it should be tender but still have a slight bite, and the sauce should have thickened to a loose, creamy consistency that coats the back of a spoon. The chicken should be cooked through and shred easily with a fork.

Finish and garnish: Remove the pan from the heat. Stir in the butter (if using) and the grated Parmesan cheese until melted and smooth. The sauce will turn a rich, pale yellow and smell intensely of lemon and cheese. Season with salt and pepper to your taste. Sprinkle the remaining lemon zest and fresh herbs over the top, and serve immediately.