Preheat oven to 425ºF. Roll out the package puff pastry dough on lightly floured board to a thickness of 1/2-inch. Using a sharp knife or cookie cutter, cut pastry into 3-inch circles.
Place on a parchment-lined baking sheet. Pierce each pastry piece several times with a fork. Brush with egg wash and bake 10 to 12 minutes until golden brown. Set aside.
Preheat oven to 375ºF. Rub and season both sides of beef medallions with 1 tablespoon of the oil, salt and pepper.
Heat 1 tablespoon butter with remaining oil in a heavy skillet over medium-high heat. Brown meat on both sides, about 1 to 2 minutes per side. Transfer to a baking sheet.
In the same skillet, melt remaining butter. Add shallots and onion and cook over medium-high heat, stirring, until softened for about 1 minute. Add mushrooms and cook, stirring occasionally, until there is no liquid from the mushrooms remaining, about 5 to 10 minutes. Season to taste. Set aside to use for Madeira Mushroom Sauce.
Top each medallion with pate slices and mushroom mixture. Bake in oven for 8 to 10 minutes to finish. Serve with Madeira Mushroom Sauce and 1 to 2 Wellies.
Madeira Mushroom Sauce
Place skillet used to make mushrooms over medium-high heat. Stir in 4 cups of beef brother, stirring up brown bits from the bottom of the pan.
Bring to boil and cook for 15 to 20 minutes to reduce to 1-2/3 cups. Stir in 2/3 cups Madeira and continue to boil until liquid is reduced again to 1-2/3 cups about 5 minutes.
Stir in a generous splash of whipping cream to finish. If desired, thicken by stirring a mixture of 1 tsp corn starch with 1 tsp cold water. Cook 3 to 4 minutes until slightly thickened. Season with salt and pepper to taste. Pour into gravy boat and serve.
Place skillet used to make sauce over medium-high heat. Stir in 1 tbsp butter and 1 tsp chopped garlic. Cook for 1 minute.
Add 4 cups baby spinach. Stir to cover with butter for 30 seconds. Turn off heat, cover and allow spinach to wilt.