True to its name, the matambre, or "hunger killer," will satisfy the heartiest appetite and can be served hot or cold. For best results, marinate meat the night before.
3 lb. flank steak
1/2 cup red wine vinegar
1 small onion, finely chopped
2 garlic cloves, minced
1 tbsp. finely chopped serrano chile (optional)
4 to 5 sprigs parsley, coarsely chopped
1 tsp. dried thyme
4 tsp. salt
2 large carrots
1 cup breadcrumbs
3 tbsp. milk
1/2 lb. fresh spinach, trimmed
4 hard-boiled eggs, peeled and quartered
1 large onion, sliced into 1/8-inch-thick rings
1 1/2 cups water
1 bay leaf
1. Butterfly flank steak, slicing it in half horizontally, with the grain, to within 1/2 inch of far lengthwise side (or ask your butcher to do it for you) so that steak opens up like a book. Using meat mallet, pound opened steak until it is 1/4 inch thick.
2. In a large bowl, combine vinegar, onion, garlic, chile, parsley, thyme, and 1 teaspoon of the salt. Drop steak into mixture and rub well on all sides. Cover and refrigerate at least 4 to 5 hours or overnight.
3. Halve each carrot lengthwise, then cut each half into 4 lengthwise strips; set aside. Moisten breadcrumbs with milk, stirring well to make a granular mixture, and set aside.
4. Preheat the oven to 350°F.
5. Drain steak, reserving marinade. Sprinkle remaining 3 teaspoons salt over opened steak and then sprinkle with breadcrumb mixture. Layer with spinach and arrange carrot slices over width of steak. Place egg wedges between carrot slices, and top with onion rings. Carefully roll steak jelly-roll fashion to cover filling completely. Secure steak with string tied at 1-inch intervals. Tie 2 pieces of string lengthwise along steak to secure further and keep filling intact.
6. Place rolled steak in large baking dish or Dutch oven. Add 1 1/2 cups water, bay leaf, and reserved marinade. Cover well with foil or lid and bake for 1 hour. Uncover and bake another 10 minutes. Transfer to cutting board and let cool 10 minutes before cutting into 1/2- to 1-inch-thick slices. Serve moistened with a bit of cooking juices from pan.