Chicken: Pat 2 chicken breasts dry and season both sides with 1 tsp salt and 1 tsp pepper. Heat a grill pan to medium-high heat and add 2 tsp olive oil. Grill the chicken for 5-6 minutes per side, or until cooked through. Remove and let rest for a few minutes before slicing.
Courgette: Grab a large pan and melt 6 tbs butter over medium-high heat. Add 4 tsp crushed garlic and stir for 1 minute. Slice 2 courgettes and add to the pan, along with 1 tsp salt and ¼ tsp chilli flakes. Cook for 5 minutes, then start the pasta. Once the pasta is cooking, continue cooking the courgette for a further 8-10 minutes until the liquid releases and cooks off and the courgette turns soft and concentrated. Reduce the heat if it starts to brown. Mash the courgette down into smaller pieces with your spoon until it's almost spreadable.
Pasta: Bring a large pot of salted water to a boil and cook 200g spaghetti as per packet instructions. Before draining, scoop out 1 cup of pasta water and set aside.
Finish: Pour in ½ cup of the reserved pasta water to the courgette pan and mix. Add the drained spaghetti and cook together for 2 minutes, tossing with tongs to coat the pasta in the courgette butter, adding more pasta water as needed to loosen. Toss through half of ½ cup grated parmesan and a handful of sliced basil.
Serve: Transfer to a serving bowl, top with sliced grilled chicken, and finish with the remaining parmesan and fresh basil.