Place flour in a shallow dish. Lightly dredge each chicken thigh in the flour. Discard the remaining flour.
Heat 1 teaspoon oil in a large skillet over medium-high heat. Add the chicken and cook until golden, 2 to 4 minutes per side. Transfer to a plate, cover and keep warm.
Reduce heat to medium-low and add the remaining 2 teaspoons oil to the skillet. Add onion, mushrooms and rosemary and cook, stirring often, until the vegetables are lightly browned, about 5 minutes. Add tomatoes, white wine, salt and pepper and cook until the onion is very soft, about 5 minutes. Return the chicken to the pan, nestle into the sauce, reduce heat to a simmer and cook until the sauce is thickened and the chicken is cooked through and no longer pink in the middle, about 5 minutes. Sprinkle with parsley and serve.