For the crust, cut the cold butter into small cubes and freeze for 20 minutes.
Meanwhile, prepare the filling. Slice the zucchini very thinly and spread on a clean kitchen towel. Sprinkle over some salt, covet with another clean kitchen towel and set aside. This will draw a lot of moisture out of the zucchini.
Peel and wash the corn then slice down the cob with a sharp knife to cut off the kernels.
Melt two teaspoons of butter on a frying pan on medium heat. Add finely chopped shallot and corn kernels and saute for 3 minutes. Set aside to cool.
Place the frozen butter cubes, flour and salt in a food processor and pulse a few times to mix, until the butter resembles small clumps.
Add a tablespoon of ice-water at a time and pulse until it starts to come together, taking care not to overwork it. It will be very crumbly still, at this point.
Tip dough onto your work surface and gather into a heap, form a ball, then flatten, before wrapping it in clingfilm. Chill in the fridge for 1 hour, until firm.
Heat oven to 200 C / 180 fan / 400 F /gas mark 6 and line a large baking sheet with parchment paper or a silicon baking mat; set aside.
In a medium bowl, mix the crème fraîche and the parmesan. Add lemon zest, season and fold in the corn.
Once pastry dough has chilled, roll the dough into a 12-inch circle between two pieces of non-stick parchment paper. Gently transfer and flip the dough over onto the pre-lined baking sheet.
Spoon cream and corn filling into the centre about 2 inches from the edge. Top with zucchini slices in an attractive pattern. Fold the crust upward and onto the sides of the filling creating pleats about every 1 ½ inches.
Whisk the egg in a small bowl and brush lightly all over the crust.
Bake for 25 to 30 minutes until the crust is golden. Remove from the oven and allow to rest over a wire rack for 10 minutes before slicing. Enjoy!