Put the chicken strips with the garlic and half the lemon rind and juice in a non-metallic bowl and turn to coat in the marinade. Cover and leave to marinate in a cool place for 15 minutes.
Heat the oil in a large frying pan over a high heat. Season the chicken with salt and pepper, add to the pan and cook, stirring, for 2 minutes. Add the broad beans and cook, stirring, for a further minute until the chicken is golden and cooked through. Stir in the crème fraîche, tarragon and remaining lemon rind and juice. Season with salt and pepper and remove from the heat immediately the sauce reaches boiling point.
Cook the pasta in a large saucepan of salted boiling water until al dente: according to packet instructions for dried pasta or for 2 minutes if you are using fresh pasta. Drain thoroughly, reserving a ladleful of the cooking water.
Tip the pasta into the sauce and toss over a low heat until well combined. If the sauce looks too dry, add a little of the reserved pasta cooking water to give it a silky consistency.