FOR THE CHICKEN LIVER PATE: In a skillet, place 2 tablespoons butter and 1 small thinly sliced onion and saute until golden brown.
Add the 6 tablespoons of schmaltz (chicken fat) and mix real well as you crumble the onion slices.
This is called schmaltz with grieven.
You can use this right away; however, it is better to make this a couple of months ahead of time and place it in the freezer to cure.
When ready to make the pate, in a skillet saute the onions in the vegetable oil over a medium flame until golden brown and add the schmaltz with grieven.
Boil the 4 eggs until hard boiled.
Add the chicken or goose livers to the pan with the onions, grieven and garlic and cook 2 or 3 minutes until done.
Add the cream sherry and cook an additional minute.
Remove from pan and allow to cool.
In a food processor, gently PULSE the livers and hard boiled eggs into a rough chop.
DO NOT OVERMIX!
Add salt, pepper, garlic powder and sugar and adjust as necessary.
FOR THE BEEF WELLINGTON: Preheat oven to 400 degrees.
Season roast with salt, pepper, garlic powder and basil to taste. On a rack, in an uncovered roasting pan, roast filet, with suet on top, in middle of oven for 30 to 45 minutes or longer, until a thermometer registers 120 degrees.
Allow filet to cool completely and discard larding fat and strings if strings are there.
Skim the fat from the pan juices and save the juices. In a heavy skillet, saute the finely chopped mushrooms in the butter over medium-low heat, stirring until all the liquid is evaporated and the mixture is dry.
Season with salt and pepper and allow to cool completely.
Spread the pate evenly over the top and sides of the filet, and then spread the mushrooms evenly over the pate.
On a floured surface, roll the 1 lb. of puff pastry into a rectangle large enough to enclose the filet completely, which should be about 20 x 12 inches.
Invert the coated filet very carefully onto the middle of the dough and fold up the long sides of the dough to enclose the filet.
With your finger you can make criss-cross grooves in the dough as a decoration.
Brush the edges of the dough with egg white to seal.
Repeat with the ends of the dough.
Transfer the filet, seam down, to a jelly roll pan or a shallow roasting pan and brush with egg wash.
Chill for 1 hour, but not more than 2 hours.
Make sure that oven is preheated to 400 degrees and bake the filet in the middle of the oven for 30 minutes.
Reduce the heat to 350 degrees and bake for 5 to 10 minutes longer, or until a meat thermometer registers 130 degrees for medium-rare.
Remove from oven and allow to rest for 15 minutes.
In a saucepan, boil the reserved pan juices and Madeira Wine until the mixture is reduced by one quarter.
Add the arrowroot, beef broth, salt and pepper.
Cook over medium heat, stirring (being careful not to boil) for 5 minutes or until thickened.
Loosen the filet from the jelly roll pan and transfer with 2 spatulas to a heated serving platter.
To serve, cut the filet into 3/4 inch thick slices and dress with the sauce.