Peel the potatoes and, on a cutting board using a sharp knife, cut them into wedges.
On a cutting board, halve the leek lengthwise and slice it thinly. Finely chop the onion and garlic.
Place a large, deep non-stick pan over high heat and add 2 tablespoons of olive oil.
Sear the chicken thigh fillets well on all sides until nicely browned, seasoning with salt and freshly ground black pepper.
Remove the chicken from the pan and transfer it to a bowl. Return the pan to high heat and add the remaining olive oil.
Sauté the leek, onion, and garlic for 3–4 minutes, stirring well, until softened and lightly caramelized without browning.
Deglaze with the white wine and, once it has evaporated, add the chicken back to the pan along with the potatoes. Sprinkle with the flour and stir well until the flour is no longer visible.
Add the chicken stock, salt, and freshly ground black pepper, and mix well. Once the dish comes to a boil, reduce the heat, cover, and let it simmer gently for 25–30 minutes.
When the dish is ready, add the lemon juice, lemon zest, and dried oregano, and stir well.
Serve on large individual plates, drizzling with a little olive oil on top.
