Prepare the beef: Mix the olive oil, sliced garlic and marjoram in a baking dish. Add the beef and turn to coat, then cover and marinate at room temperature, turning occasionally, 1 hour.
Meanwhile, make the skordalia: Smash and peel the garlic cloves; warm in a small saucepan with the olive oil over low heat until soft, about 12 minutes. Meanwhile, peel the potato and cut into chunks. Cover with water in a saucepan, season with salt and simmer over medium heat until tender, about 12 minutes. Transfer the potato to a bowl with a slotted spoon, reserving the cooking water, and mash with a potato masher.
Blend the almonds in a food processor until smooth. Add about half of the softened garlic, 1/2 cup of the garlic-flavored oil, 1/3 cup potato cooking water, the vinegar and 3/4 teaspoon salt; puree until smooth. Add the potato and pulse just until creamy. Transfer to a bowl and stir in the marjoram and parsley.
Preheat the oven to 400 degrees F. Remove the beef from the marinade and scrape off any garlic (reserve the marinade). Heat a large ovenproof skillet over medium-high heat. Add 1 tablespoon of the marinade, then sear the beef until browned on all sides, about 8 minutes. Transfer the skillet to the oven and roast until a thermometer inserted into the center of the beef registers 125 degrees, about 15 minutes. Transfer to a cutting board and let rest 10 minutes.
Slice the beef and serve with the skordalia. Top with the remaining garlic oil, softened garlic and more marjoram.
Photograph by Con Poulos
Recipe courtesy Food Network Magazine