Cook the gluten free pasta in boiling water for 8-10 minutes, or according to packet instructions, until just tender.
Meanwhile, heat the oil and fry the chicken over a high heat for 4-5 minutes, stirring, until golden and cooked. Add the garlic oil, cream, tarragon and 3 tbsp of the pasta cooking liquid. Gently heat through.
When the pasta is cooked, stir in the spinach (it will immediately wilt in the hot water). Drain well, then toss into the creamy chicken. Season with salt and pepper and serve with lemon for squeezing.