In small saucepan, combine 8 tablespoons butter and milk, place over low heat until lukewarm, stirring to melt the butter. Remove from heat and allow to cool.

In a large bowl, combine 5 cups flour, sugar, salt and yeast.

In a medium bowl, beat eggs lightly, and then whisk in milk mixture.

Using a mixer with a dough hook, or by hand, stir liquid ingredients into dry ingredients.

Knead dough for 7-8 minutes until smooth and springy, adding more flour by the tablespoon if necessary to form a soft, slightly sticky dough.

Form into a ball, and place in an oiled bowl. Cover with plastic wrap, and let rise in a warm place until double in size, about 30 minutes.

Line bottom of a 13-by-10-inch baking pan with parchment paper. Punch down the dough.

On a lightly floured surface, roll out dough to a rectangle about 22 by 12 inches.

Dollop remaining 8 tablespoons softened butter over dough and spread into an even layer. Sprinkle the sugar evenly over the butter.

Chop pistachios until splintery, and sprinkle evenly over dough. Top with chocolate chips, pressing the chocolate and nuts gently into the dough.

Starting from longest side, carefully roll up dough so it looks like a long sausage. Cut dough into 20 slices, 1-inch thick, arrange with a cut side up in pan.

Position a rack in the center of the oven and preheat oven to 400 degrees.

Brush buns with beaten egg, and let them sit in a warm place until puffed and spongy, about 15 minutes.

Bake until buns are risen and golden brown, 25 to 30 minutes.

Let cool in the pan at least 30 minutes, then cut and serve warm.