1] Place the butter, horseradish, Dijon mustard, shallots, salt and pepper in the stainlesssteel bowl of an electric mixer fitted with a paddle attachment. Mix on low speed until blended. \
2] Place 1-lb. portions of butter on sheets of parchment paper and roll into 2" cylinders.
3] Wrap the rolls in plastic to preserve their flavor. Refrigerate until needed.
1] Slice the Dijon Shallot Butter into 1" thick pieces. Place in a stainless steel mixing bowl and cover with film wrap. Allow to come to room temperature.
2] Remove all of the fat and silver skin from the strip loin. Wrap the meat in film wrap and place in the freezer for about 1 hour or until it is firm enough to slice.
3] Place the strip loin on an electric slicer with the best end down so it can be sliced against the grain. With the slicer at the 7½ setting, slice into 10 1-oz. slices. Lay the slices on a parchment-lined sheet pan in a single layer.
4] Lay a piece of beef out flat on a film-wrapped, rimless metal baking pan. When assembling, don’t press down on the layers. Spread ¾ to 1 oz. of Dijon shallot butter over the beef to cover evenly. Carefully lay a second piece of beef on top of the first layer of butter. Spread 1 oz. of butter on top of the beef. Repeat with the other 8 beef slices to create a stack with 9 layers of butter and 10 layers of beef. Cover with film wrap and refrigerate for 24 hours.
5] Slice the bread into ½-oz. pieces widthwise. Place side by side on a parchment-lined sheet pan. Place in a heated 300°F convection oven for 6-7 minutes or until they just begin to brown. Lower the temperature to 225°F. Cook another 8-10 minutes or until crunchy. Allow to cool. Place in a storage container. Cover until needed.
To prepare à la carte:
1] Slice 3 pieces of the layered beef-and-butter widthwise. They should weigh a little less than ¾ oz. so the three pieces weigh 2 oz. total.
2] Place the slices on the front of a chilled serving plate so the are not touching. Sprinkle coarse black pepper and the fleur de sel to taste over the carpaccio butter. Place 7 bread rounds on the plate next to the carpaccio butter.