Put the flour, sugar, yeast and salt in the bowl of a stand mixer fitted with a dough hook and mix. Using a fork, beat together the eggs and milk then, with the mixer on a slow speed, pour the mixture into the flour.
Once incorporated, keep the mixer running and add the butter in 4 additions, making sure it’s completely incorporated before adding the next bit; keep scraping the dough down from the sides of the bowl with a spatula, if necessary.
Knead on a medium speed for 5 minutes. Scrape the dough into a ball and leave in the bowl, covered with cling film (plastic wrap), to rise until doubled in size. This could take 1 hour on a warm day, or up to 2 hours on a cool day (or you can chill it overnight at this stage, letting it come back to room temperature, out of the fridge, before continuing).
Line a large baking tray (pan) with baking parchment. Knock back the dough and divide it into 6 pieces (roughly 90 g/3 oz each). On a lightly floured surface, roll out each piece to form a 10–12 cm (4–5 in) circle. Place on the prepared baking tray. Cover with cling film and leave to prove for about 1 hour, at room temperature, until slightly puffed up.
Preheat a fan oven to 160˚C (320˚F/gas 4). Brush the tops with the egg yolk, then sprinkle over the sugar. Arrange the sliced peaches on top, then bake for 10–12 minutes, turning the tray halfway if they brown more on one side than the other. Remove from the oven. These are best eaten the day they’re made, but can be stored in an airtight container and warmed in a low oven the next day.