For the stuffing with sun-dried tomatoes & pesto sauce:
Mince the sun-dried tomatoes. Spread the puff pastry on the kitchen worktop and spread the pesto sauce all over. Divide the sun-dried tomatoes, 2 tbsp ground hard Danish cheese and the pepper equally on the pastry.
Roll it along its longer side and towards the sheet center. Repeat on the other side, like two rolls joined tightly at the sheet center. Place the roll in the fridge for 30 min. Smear the roll with the egg yolk all around and cut in 20 slices with a sharp knife.

For the stuffing with prosciutto:
Spread the pastry sheet. Spread the mustard all over. Add the prosciutto slices and sprinkle 2 tbsp from the hard Danish cheese on top. Roll the sheet from both sides towards the center. Place it in the fridge for 30 min. Smear the sheet with the egg yolk and cut it in 20 slices.
Lay the sheet on a buttered baking sheet and bake the palmiers at 200°C in air for 10 min, until golden brown. Once baked, take them out of the oven and sprinkle the remaining cheese on top.