In a bowl, combine the flour, yeast, salt, turmeric, oil, cheese, and milk. Knead until you get a smooth dough and let rest for 15 minutes. Roll out the dough with a rolling pin to a thickness of half a centimeter, cut into triangles, place a cube of fontina and some mushrooms at the base of each triangle, then roll them up to form croissants. Brush with the egg yolk mixed with a little milk and sprinkle the surface with sesame seeds. Bake at 180°C (356°F) for about 20 minutes.