Start the day before, or atleast early in the day to serve in the evening. The dry ingredients need time to soften, and get friendly. Mix all ingredients and refrigerate over night.
Carve out the bread to make a bowl, saving the bread to dip into the sauce.
When ready to serve, put the dip inside the bread, arange the bread pieces around the 'bowl'. When the pieces are gone, slice, rip, or tear the remaining crust and eat.
We had a bakery in Baltimore that made a great Sweedish/Onion Rye, although that was the name on the bread, they claimed that there was nothing special about it. I have served it with plain 'store bought' rye, the round loaves and with my own home made rye.