Preheat the oven to gas 6, 200°C, fan 180°C.
Roll out the pastry on a lightly floured surface to 1cm thick and cut rounds of pastry slightly larger than the fluted mini tart tins. Line the fluted mini tart tins using the pastry, pressing in well and prick the bases. Trim any overhanging pastry and chill for 10 minutes. Fry the vegetables in the sunflower oil in a frying pan for 4-5 minutes until soft over a medium heat, then remove from the heat.
Line the pastry cases with nonstick baking and fill with baking beans. Bake in the oven on a baking sheet for 10-12 minutes until golden. Remove the paper and beans at this point, brush the bases with the beaten egg yolk and return to the oven to allow the base to cook and brown.
Meanwhile, make the filling by whisking the crème fraîche and the milk together. Beat in the eggs one at a time and season well with salt and pepper. Remove the pastry cases and pour the filling into each one so that it comes three quarters of the way up. Arrange the grated cheese and vegetables to each one and return to the oven on a baking sheet.
Bake at 170°C for 20 minutes until the filling has just set. Remove and serve immediately with the rocket on the side as a garnish.