- Preheat the oven to 350°.
- Place the potatoes, leeks, and olive oil in a mixing bowl and season with salt and pepper.
- Gently toss to mix well. Transfer to a 6 by 9-inch baking dish and pat gently to form an even layer.
- Cover the dish with foil and bake in the oven for 1-1/2 hours or until the potatoes are tender.
- Let cool completely, cover with plastic wrap, and chill.
- When ready to serve, preheat the oven to 450°.
- Cut the potatoes into 4 even sections.
- Using a metal spatula, transfer the squares to a rimmed baking sheet.
- Bake in the oven for 30 minutes or until the tops are browned.
- Melt the butter in a saucepan and sauté the mushrooms over medium-high heat for about 5 minutes or until lightly golden.
- Add the flour, season with salt and pepper, and stir well. Stir in the cream and keep warm.
- Melt the 1 tablespoon butter in a sauté pan or cast-iron skillet.
- Season the filets with salt and pepper.
- When the pan is hot, sear the filets over high heat for 2-1/2 to 3 minutes on each side for medium-rare, about 4 minutes on each side for medium, or to the desired doneness.
- Remove the steaks from the pan and just before serving, stir the whiskey into the pan juices.
- Bring to a boil and cook for 2 minutes or until the alcohol burns off.
In a separate sauté pan, melt the 4 tablespoons of butter and sauté the bread slices over medium-high heat, turning often so the bread becomes crispy and not soggy, about 3 or 4 minutes. Transfer to a serving platter, top with the filets, and arrange the mushrooms in the center. Spoon the whiskey sauce over the filets and serve with the potatoes.