Cut butter into pieces. Knead flour, butter, 1 pinch of salt and 1 egg with the dough hooks of the hand mixer. At the end use your hands to knead into a smooth dough. Wrap the dough in cling film and chill for about 20 minutes.
Peel carrots and put 1/2 carrot aside. Halve the rest lengthwise and cut into small diagonal pieces. Clean and wash spring onions and cut into slanted rings. Mix 4 eggs and milk and season to taste with salt, pepper and nutmeg.
Simmer carrots for about 3 minutes, drain and rinse in cold water. Cut feta cheese into small cubes. Roll out the dough thinly on a floured work surface and cut out circles (approx. 13 cm Ø).
Knead the remaining dough again and cut out a total of 8 circles. Grease 8 tartlet moulds (approx. 11 cm Ø) with removable base and insert one circle of dough each. Spread the carrots and spring onions on the tartlets.
Pour the egg milk up to the rim. Cover with the feta cubes. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 20-25 minutes. Score the carrot aside 5 times lengthwise with a Juliet chiseler and then cut into slices.
Take the ramekins out of the oven. Carefully lift the bases out of the ramekins. Garnish the tartlets with the carrot slices and parsley.