Preheat the oven to 200C/(180C fan)/390F/gas 6. Tip the squash or pumpkin, rosemary, chilli flakes, sea salt flakes and olive oil into a large, deep roasting tin. Mix well, then transfer to the oven to bake for 25 minutes, until just softening.
Place the kale into a large bowl, and cover with boiling water. Leave to sit for two minutes to blanch, then drain well and set aside.
Put the gnocchi into the bowl you just used for the kale, and cover with another kettleful of boiling water. Leave to sit for two minutes to blanch, then drain well.
Once the squash has had 25 minutes in the oven, remove from the oven and gently stir through the blanched kale, gnocchi and creme fraiche until evenly mixed. (It doesn’t matter that the gnocchi won’t sit all in one layer, as this is a gratin-style dish.)
Scatter over the feta cheese, then a big handful or so of panko breadcrumbs and a good amount of freshly ground black pepper. Drizzle with a little olive oil if you wish, then transfer to the oven to bake for 30 minutes, until golden brown and crisp on top.
Serve hot, with some roasted cherry tomatoes or a green salad on the side if you wish.