Preheat the oven to 200°C.
Roll out the pastry on a lightly floured surface to 1cm thick and cut rounds of pastry larger than mini cheesecake moulds with dimensions of roughly 5cm in width and 5cm in depth.
Line the base and sides of the mini cheesecake moulds using the pastry, pressing in well and pricking the bases. Trim any overhanging pastry and chill for 10 minutes.
Line the pastry cases with nonstick baking paper 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 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, mint and petit pois in each one and return to the oven on a baking sheet. Bake at 170°C for 12-15 minutes until the filling has just set.
Remove from the oven and allow to cool on a wire rack for a few minutes before attempting to turn the quiches out. Place on mini saucers when ready to serve.