4 tablespoons extra virgin olive oil (EVOO), divided
1 pound good quality marbled steak, such as sirloin, thinly sliced into bite-size pieces
Salt and ground black pepper
4 Idaho potatoes, scrubbed clean and very thinly sliced into rounds
1 large onion, thinly sliced
2 garlic cloves, grated
1 bottle dark beer, such as Guinness
2 tablespoons Worcestershire sauce
4 cups beef stock
1 cup crème fraiche or sour cream
2 tablespoons chopped chives
1 tablespoon prepared horseradish
1 small bunch watercress or arugula, roughly chopped, to garnish
Place a large pot over high heat with 2 turns of the pan of EVOO, about 2 tablespoons. When the pan is scorching hot, season the beef with salt and pepper and add it to the pot. Cook the meat, stirring occasionally, until deep golden brown and cooked through, about 5 minutes. Remove from the pot and reserve on a plate. To the same pan the beef was cooked in, add the remaining EVOO (about 2 turns) along with the potatoes, onion and garlic. Season the veggies with salt and pepper and cook, stirring occasionally, until the onions are tender, 6-7 minutes. Add the bottle of beer to the pot and scrape the bottom to remove any brown bits that have stuck. Add the Worcestershire and beef stock, and bring the liquids up to a bubble. Simmer the stoup until the potatoes are tender, about 5 minutes.
While the stoup is simmering, stir together the crème fraiche or sour cream, chives and horseradish in a small bowl. Reserve.
When the potatoes are tender, stir the steak back into the stoup and portion it into bowls. Garnish each bowl with a dollop of the horseradish-cream mixture and some chopped greens, and serve.