Bring a large saucepan of salted water to the boil for spaghetti. Cut the unpeeled pumpkin into 2cm chunks (see cooking tip). Tear the kale leaves into small pieces, discarding the stems. Quarter the zucchini lengthwise and cut into 1cm chunks. Crumble 1 stock cube* into a heatproof jug, add 250ml (1 cup) boiling water and stir to dissolve.
Step 2 — Brown chicken
Heat 2 tsp olive oil in a medium deep frypan over high heat. Season the chicken with salt and pepper. Cook the chicken for 2 mins each side or until golden (the chicken won't be cooked through). Remove from the pan and reserve the pan.
Step 3 — Cook spaghetti
Add three-quarters of the spaghetti* to the pan of boiling water (if you're tempted to throw in all the spaghetti, just note the dish won't be as saucy). Cook, stirring occasionally, for 12 mins or until al dente. Drain. Reserve 2 tbs cooking water, then drain the spaghetti.
Step 4 — Cook pumpkin
Meanwhile, add the pumpkin, stock, Italian seasoning and a pinch of chilli flakes* (if preferred, omit the chilli) to the reserved frypan and bring to the boil. Reduce the heat to medium and cook, covered, stirring occasionally, for 7 mins.
Step 5 — Finish chicken
Add the kale to the pumpkin and cook, uncovered, stirring regularly, for 2 mins. Add the zucchini and chicken and cook, stirring occasionally, for a further 4 mins or until the vegetables are tender and the chicken is cooked through. Remove the chicken from the pan using tongs, then cut into chunks. Finely grate the parmesan.
Step 6 — Get ready to serve
Stir the spaghetti, chicken, capers, half the parmesan and 15g butter into the pumpkin mixture. Gradually add the reserved cooking water, stirring constantly, until the sauce coats the spaghetti and looks slightly glossy. Taste, then season with salt and pepper. Divide the spaghetti among bowls and scatter with the remaining parmesan to serve.