1. Preheat your oven to 180°C/Fan 160°C/Gas 4. Put a large pan of salted water on to boil.
2. Get the veg prepped:
Slice the leaves off the cauliflower then chop the cauliflower into small florets and the stalk into bite-sized pieces. Set aside. Trim the roots and top 3cm off the leeks. Slice a cross in the tops of the leeks, open them out and rinse out any grit. Finely slice the leeks. Snip and chop the sun dried tomatoes into thin strips. Trim the dry ends off the cavolo nero, then finely slice the leaves.
3. Start the cheese sauce:
Put a medium pan on a medium heat and add the butter. Swirl it around to melt the butter, then add the leeks with the bay leaf and a pinch of salt and pepper. Fry, stirring often, for 5 mins till the leeks look glossy and are lightly browned.
4. Add 2 tbsp flour to the leeks and cook, stirring, for 2 mins. Measure out 800ml of the milk. Add a splash of the milk and stir it into the leeks and flour till combined, then carry on adding splashes of milk, stirring well between each addition, till all 800ml has been added. This should take around 5-6 mins. This is your white sauce.
5. Once you’ve added all the milk, drop in the cavolo nero. Let the white sauce come up to a bubbling simmer. Don’t let it get too hot or it will boil over. As soon as it’s bubbling, turn the heat down to low and simmer for 3-4 mins, stirring often, till the sauce starts to thicken a little and the cavolo nero wilt.
6. Cook the pasta & cauliflower:
When the pan of water is boiling, add the gnocchetti pasta. Simmer for 6 mins, then add the cauliflower and sun dried tomato strips and simmer for 3 mins till the pasta is tender but still has some bite.
7. Finish the cheese sauce:
While everything simmers, coarsely grate the cheddar. Once the white sauce has started to thicken (if you stir it with a wooden spoon, you should just see some trails in the sauce), take it off the heat. Fish out the bay leaf. Add 3/4 of the cheddar and grate in plenty of nutmeg. Taste the sauce and add more salt, pepper or nutmeg if you think it needs it.
8. Into the oven:
Tip the pasta and veg into a large ovenproof dish. Pour over the cheesy white sauce and stir gently to mix. Sprinkle over the breadcrumbs and top with the last of the grated cheddar. Slide into the oven and bake for 15 mins. Remove from the oven, sprinkle over the pine nuts and bake for another 5 mins till golden and bubbling. Serve in warm bowls.