Season the chicken on both sides with salt and pepper. In a 30 cm Iron Handle Skillet over medium heat, cook the chicken in half of the oil for 4 minutes on each side or until nicely browned. Set aside on a plate.
Add the remaining oil and the leek to the s killet. Season with salt. Cook over medium heat, stirring, until tender and starting to brown, about 3 minutes. Add more oil as needed. Add the garlic and red pepper flakes. Cook for 1 minute while stirring. Add the wine and let reduce for 2 minutes.
Add the cream, chicken stock, Dijon and lemon zest to the Skillet. Season with salt and pepper. Mix well to combine. Bring to a boil. Add the spinach and simmer for 2 minutes. Stir in the lemon juice, basil and tarragon. Adjust the seasoning.
Return the chicken to the Skillet and stir to coat in the sauce. Cook for 2 minutes longer or until the chicken is cooked through. Place the Skillet at the centre of the table. Delicious served over short pasta.