Mix the warm milk, melted butter, granulated sugar, and instant yeast in a bowl. Let sit for 5 minutes.
Combine the egg yolk, flour, and salt into the wet ingredients, stirring until a shaggy dough forms.
Knead the dough on a lightly floured surface for 5 minutes until smooth and elastic, then let it rise in a covered bowl for 1 hour.
Roll the dough out into an 8x6 inch rectangle.
Spread the softened butter, pistachio cream, and brown sugar evenly over the dough surface.
Shape by rolling the dough tightly into a log, cutting it into 4 equal slices, and placing them in a greased 6-inch baking dish. Let rise for 30 minutes.
Bake at 350 degrees Fahrenheit for 20 minutes. Whisk the cream cheese and powdered sugar together, then spread over the warm rolls.