Preheat the oven to 275°C/350°F and grease the inside of an 8″ loose-bottomed cake tin with butter. Through in the cornmeal and shake until the bottom and sides of the tin are covered. Set aside.
Bring a large pot of water to the boil and salt it well. Add the cauliflower florets and boil for 2 minutes; add the broccoli and continue cooking for another 90 seconds. Drain and rinse the vegetables well in cold water.
Head the butter and olive oil in a nonstick pan over medium heat. Sauté the leeks for 8-10 minutes until very soft but not yet browned. Set aside to cool.
Whisk the eggs together in a large bowl until well beaten. Add the flour, baking powder, spices, salt and lots of black pepper, and whisk well. Add the cheeses and cooled leeks, and whisk again. Stir in the cauliflower and broccoli florets until well coated; feel free to break up any too-large florets with a wooden spoon.
Pour the mixture into the prepared cake tin and spread evenly. Bake for 25-30 minutes until puffy and golden on top. The cake will feel firm to the touch when done. Let cool at least 10 minutes before gently un-moulding and slicing.
