Preheat your oven to 220°C (200°C fan).
Heat a large frying pan over a medium heat and add the olive oil. When hot add the leeks and red onion and sauté for about five minutes until soft.
Add the garlic and cook for another minute.
The kale likely won't fit in the pan all at once, so add couple of handfuls at a time. When cooked down add more.
While the kale is cooking down make the tomato sauce. To drain the plum tomatoes place them in a sieve over the sink to get rid of the more watery liquid. Add the tomatoes along with the rest of the sauce ingredients to a food processor and blitz until smooth. Pour the sauce into a bowl and give the food processor bowl a quick rinse.
Once all your kale has cooked down place all the vegetable mixture into the food processor along with the cottage cheese. Pulse a few times until the mixture is blitzed together, but don't blend until completely smooth - keep some texture. Add salt to taste.
Now to assemble. Spread a couple of spoonfuls of the tomato sauce on the bottom of the dish (I use a 9"x9" dish). Add two lasagne sheets (or, depending on the size of your sheets, however much to cover the bottom), then a third of the green mixture, spread out a layer of tomato sauce on top, and sprinkle some cheese. Repeat two more times using up the rest of the green mixture. For the top layer, use the remainder of the tomato sauce and spread out across the lasagne sheets followed by the remainder of the cheese.
Cover your dish with a lid or foil and bake for 20-25 minutes. Remove the lid/foil and bake for 10-15 minutes more, until it starts browning on top.
Remove for the oven and let cool for about 10 minutes before serving.