The French restaurant Les Valseuses (located in Prenzlauer Berg, close to U Eberswalder Straße) was highly recommended to me, especially for their steaks. They have a small fixed menu, with a few starters and the beef (rumpsteak, entrecote and tartare), plus starters and mains and desserts that change daily, although I think the chocolate fondant is always there.
I was very warmly welcomed, the staff is extremely friendly. The waiter was kind enough to make me a special (uncomplicated) cocktail (Tequila Sunrise) whereas they normally do only long drinks. I had the duck rillettes as a starter, surprisingly a bit spicy but still very tasty. Then, I went for an entrecote with blue cheese sauce… Cooked perfectly, very bloody as I wanted it, very tender, excellent meat. To end this perfect dinner I had the chocolate fondant, a bit salty, which is usually not my thing but still delicious. My friends also loved the swordfish starter, the beef tartare and the vegetarian dish (polenta and aspergus). Prices are very fair, service is good. An very nice discovery.