Preheat the oven to 200C. Line a baking tray with baking paper. Put the ricotta on this, drizzle with olive oil, grate over the zest of half a lemon, sprinkle with salt and a pinch of oregano. Bake for 30 mins or until tinged brown at the edges.
Get a large pan of salted water on to boil. When boiling furiously, add the spring onions, courgette and leek and blanch for two minutes to take the harsh notes out of the onion and start tendering the veg. Don't discard the water, now use it to cook your pasta.
While the pasta cooks, add the veg, mint, pine nuts, a swig of extra virgin olive oil and a large pinch of salt to a food processor and blitz to pieces. When everything is broken down, trickle in some more oil to make a paste. Stop the motor and grate in plenty of parmesan, lemon juice and a big splash of the pasta cooking water. Taste and add more salt, lemon or oil as required until you have a loose sauce.
When the pasta is cooked, drain and return to the pan. Toss the sauce with the pasta until well-coated. Serve in bowls, garnishing with rough chunks of baked ricotta, pine nuts and parmesan.