The concept was so simple— prix fixe steak and salad and nothing else— that the first chef at Grass Fed left almost immediately, apparently thinking there was nothing for him to do. Over time the menu has expanded slightly, but it’s still about a simple menu with just a few things on it. So what ideas can a chef contribute around the edges of a concept whose appeal is its directness? That’s the question for Jason Myers, who is joining the gleaming white Bucktown steak cafe from Deleece. His new menu launches May 1.