Season the chicken. Pat the chicken dry. Season with 1 teaspoon salt, 1/2 teaspoon black pepper, and the smoked paprika.
Toss to coat.
Brown in batches. Heat the olive oil in a large skillet or Dutch oven over medium-high heat. Add half the chicken and sear until lightly browned, about 3–4 minutes per side. Remove to a plate and repeat with the remaining chicken.
Don’t overcrowd the pan.
Sauté the aromatics. Reduce heat to medium. Add the butter. Stir in the onions and bell pepper.
Cook until softened and lightly golden, 5–7 minutes. Add the garlic and cook 30 seconds until fragrant.
Build the sauce. Sprinkle the flour over the vegetables and stir for 30 seconds. Whisk in the red wine, scraping up browned bits.
Simmer 2–3 minutes to reduce slightly.
Add flavor boosters. Stir in the chicken stock, Worcestershire sauce, tomato paste, bay leaf, thyme, and peri-peri or chili flakes. Bring to a gentle simmer.
Return the chicken. Add the browned chicken and any juices back to the pot. Reduce heat to low and simmer uncovered for 10–15 minutes, stirring occasionally, until the chicken is cooked through and the sauce thickens enough to coat a spoon.
Taste and adjust. Remove the bay leaf.
Taste and add more salt, pepper, or heat as needed. If you want a glossier finish, swirl in a small knob of butter at the end.
Serve hot. Garnish with chopped parsley. Serve with crusty bread for dipping, a pile of fries (classic), or fluffy rice.