Preheat the oven to 400F/180C.
Slice the saffron milk caps into smaller pieces and crush the garlic.
Heat the olive oil in a frying pan and add the mushrooms, garlic and a pinch of salt.
Saute for ten minutes, until the mushrooms look brown and the sauce is gone. Set aside.
Shred the cheese and split the mozzarella into small pieces by hand.
Using a pizza wheel cutter, cut the chilled puff pastry sheet into 10 squares or more, depending on the size of tarts you wish.
Place the square tarts on a baking sheet covered with parchment paper.
With a small, sharp knife cut the edges of the tarts, like forming a 1 cm wide frame. Do not cut all the way trough the pastry.
Top the middle part of the tarts with shredded cheese and add the pieces of mozzarella On top of the cheese place the saffron milk caps with garlic.
On every tart add a few drops of sour cream and black pepper.
Bake in the oven for about 20 minutes at 400F/180C until the cheese melts and gets a golden brown colour. The edges of the tarts should look puffy and medium-rare.
Enjoy your lactarius deliciosus tarts while still hot right from the oven :)