In a large container, submerge the prime in rib in 1 gallon of whole milk

Add the entire bottle of Creole butter to the milk and mix well

Using an injector, inject the milk and Creole butter mixture into the prime rib on all sides

Cover and refrigerate for 24 hours

After 24 hours, remove the prime rib from the refrigerator and dry it thoroughly with paper towels

Carefully cut towards the bone on the backside to trim off excess fat, including the fat cap

Tie the prime rib with 4 pieces of long twine to hold it together while it rests

Let the prime rib rest for 1-2 hours until it reaches room temperature

In a bowl, mix together the mayonnaise, stone-ground mustard, and Dan-O's Preem-O until well combined

Rub the seasoning concoction all over the prime rib, making sure to cover all sides and the bottom

Sprinkle additional Dan-O's Preem-O generously on top, plus a bit of Montreal Steak seasoning if desired

Preheat the oven to 275°F (135°C)

Place the seasoned prime rib in the center of a baking pan with a rack

Bake the prime rib at 275°F for 2 hours

After 2 hours, increase the oven temperature to 300°F (150°C) and cook for an additional 50 minutes

Crank the oven up to 500°F (260°C) and roast for 10 minutes to achieve a nice crust

Remove the prime rib from the oven and let it rest for 2 hours, covered with foil

Cut off the twine and slice

Serve with au jus sauce and horseradish