Preheat the oven to 180°C/350°F/gas 4. For the filling, trim the tough end off the broccoli stalk. Coarsely grate the remaining stalk, then break the florets apart. Lightly beat the eggs in a bowl, add the mustard, cottage cheese and grated broccoli stalk, grate in the Cheddar, add a pinch of sea salt and black pepper and mix together.
Loosen the pesto with 3 tablespoons of water. Lay two sheets of pastry in an oiled loose-bottomed tart tin (25cm wide, 4cm deep), overlapping them in the middle. Brush all over with some of the pesto mixture, then repeat the layers until you’ve used up all the pastry, brushing with pesto as you go. Roll and scrunch the filo in at the sides, like in the picture. Pour in the filling, then poke in the broccoli florets. Place on a baking tray and cook at the bottom of the oven for 50 minutes, or until golden and set. Let it rest for 10 minutes before tucking in.