Melt the butter in a medium saucepan and stir in the milk.

In a large bowl whisk together the warm water, yeast, and sugar. Then whisk in the egg plus egg yolks. Add the salt, 2 cups of the flour, and the butter / milk mixture. Stir with a sturdy spatula until combined.

Add the last 2 cups of flour and work it in with your hands, kneading the dough in the bowl for around 8 minutes, only adding more flour if the dough seems too sticky or wet. It should be soft, pliable, and shiny from the butter in the dough.

Shape the dough into a ball and place it into a large oiled bowl. Cover it with plastic wrap and let it rise in a warm place for 1 1/2 hours or until it doubles in size.

Butter a 9 X 13 baking dish. When the dough has doubled in size lay it on the prepared work surface and roll it out to about 16 X 12, with the longer side closest to you.

Spread the dough with the mustard and then cover it in a layer of ham slices, overlapping them. Then cover the ham with the shredded cheese.

Roll the dough up lengthwise (rolling away from you) and cut into 12 equal pieces. Lay the pieces in the prepared baking dish, cover with plastic wrap, and let them rise for another 11/2 hours.

Pre-heat the oven to 350°F.

Bake the risen rolls for 25-30 minutes. They will be golden.

While the buns bake, mix all the ingredients for the dressing together. Brush it over the hot baked rolls.