I first made the filling of these danishes as a topping for simple puff pastry rounds, served as a snack. Personally, I think it is too salty and want some brie on them to balance out the saltiness, but almost everybody seems to disagree with me, saying I should not change anything.
Ingredients:
For the croissant dough:
- 500gr strong bread flour
- 8gr dry yeast
- 10gr salt
- 50gr sugar
- 1 large egg
- 125ml cold milk
- 125ml cold water
- 250gr unsalted butter
For the filling:
- 200gr prosciutto ham
- 100ml olive oil
- 4 large cloves of garlic (or 6 regular)
- pepper
- 1 tbs fresh thyme
- 1 tbs fresh rosemary, chopped
- 2 tbs olive oil
Makes 15-16 Danishes
Recipe:
Make the croissant dough:
Mix the yeast with the flour. Add the egg, milk and water, mix quickly, then add the salt and sugar (adding salt directly to yeast will kill the yeast, which is a living organism, making bread dense and flat).
Knead the dough for a few minutes, 3-4 should do, until it becomes more elastic. You do not want to get the gluten developed much, as the rolling out later would overdevelop the gluten, making it rise less as the gluten strands will break quicker. Place the dough in a bowl, cover, and leave on a cold spot (or in the fridge) for 2 hours or overnight. Make sure the dough does not ferment, as this would cause your croissants to become doughy.
In the meantime, Place the butter between two sheets of cling film and roll it into a rectangular block that is about 1cm thick. You may want to peel off the plastic a few times and re-position it, or the plastic might rip and you could get little pieces of plastic stuck on the butter (speaking from experience). Set the butter in the fridge on a straight surface to keep it cold.
For the technique on rolling, folding and shaping croissants, more can be found in HOW TO MAKE PERFECT CROISSANTS.
Roll the cold dough out on a cold surface. In winter, I always have a window open, which works well, but you can also use a marble surface when temperatures are higher. If you do not have a stone or marble kitchen countertop, you can use a chocolate tempering block.
On a floured surface, roll the dough out – preferably with a French style, tapered rolling pin, which assists in creating a uniform thickness – into a rectangle that is the same width of the butter slab and half longer. See the sketch below. Click on the image for a larger size. 
Start with an English fold: Place the butter on the bottom part, peel off the plastic and fold the empty part of the dough over the butter, coming halfway of the butter slab. Now fold the bottom half over, with the butter. Seal the edges well to avoid butter leaking out later.
Now roll the dough out in one direction, not back and forth but only one way, then pick up the roller and start from the beginning again. Away from you tends to work best. Roll gently to form a rectangle. Too much pressure at once may cause the butter to melt into the dough, so don’t be too enthusiastic. However, don’t take forever either, especially in summer, as warmth from the outside can also make the butter melt.
Now do a book fold: When you made a rectangle, cut the edges off the top and bottom. Only a little, just to free the layers and to stop the dough from retarding the rise. Fold both cut ends to the middle, then folding one half over the other. You will have folded in 4 like this. Make two dents in the top of the dough, to remind you this was your second fold (the first was the English fold above). Place the dough on a plate or cutting board, slide it into a plastic bag and place in the fridge for 30 minutes.
Roll the dough out again lengthwise. Do another book turn, bringing the amount of butter layers to 2x4x4=32 (see the Techniques section on how to make croissants for details on the amount of layers), dent three times and then leave to rest again for 30 minutes.
Make the filling:
Place the prosciutto, garlic, oil and some pepper in a small kitchen machine. I use the attachment to my immersion blender, because a regular kitchen machine is too large. Pulse the mixture until only small chunks remain. Don’t blend to a paste.
Combine the thyme, rosemary and oil to make a herb oil.
Make the Danishes:
Line two baking trays with baking paper. Roll the dough with a French style rolling pin to a thickness of 3-4mm, preferably in a square or rectangular shape, to limit scraps. Trim the edges of the dough first, to free the butter layers and allow even expansion. Cut the dough into 15-16 squares of approximately 8-9cm. Cut instead of pushing, this will preserve the lamination that you worked so hard to achieve.
Take a square and fold it over on the diagonal. Make two cuts, a cm from the edge and leaving the last centimeter attached. Fold the dough open. Brush the dough with egg-wash, careful not to go over the edges which would seal together the layers. Fold the two flaps over to create a basket. See the sketch below for details.
Fill the cavity with a large teaspoon of ham filling. Brush the dough (not the cut edges) with egg wash. Cover the baking tray loosely with plastic, careful not to let the plastic touch the Danishes.
Leave to prove until doubled in size. This can take a while, 2 hours is normal, especially because you do not want to prove them in a very warm environment because of the butter. A slow prove will yield better results.
Underproofed Danishes will not rise much, because the butter will leak out and cannot create the steam to puff the layers up. The Danishes should be very soft, puffed up and jiggly. In a relatively cool spot they will not easily overproof.
Divide the herb oil over the ham in the Danishes. Egg-wash again (not over the cut sides), then slide the Danishes into an oven that has been pre-heated to 210°C. Bake for 5 minutes, then turn the temperature down to 190°C and bake for 10 more minutes, or until dark brown and crisp.