Heat the oven to 180C/160C fan/gas 4. Butter and line a 23cm round deep, springform cake tin so the paper comes 2-3cm up the sides of the tin.

Melt the butter in a frying pan. Add the onion and pancetta and cook over a low heat for 10 mins or until softened and translucent.

Bring a pan of lightly salted water to the boil. If using broccoli, cut into small florets, if using asparagus, keep whole. Blanch the veg for 2 mins, drain and leave to steam-dry.

Whisk the eggs, cream and two thirds of the cheese together in a bowl. Season with salt and black pepper. Mix through the onion and bacon mixture. Pour into the tin and top with the veg and remaining cheese. Bake for 25-30 mins or until golden brown with a slight wobble in the centre.