How do I score a bâtard to achieve this effect?

At first, it looks like a simple slash down the center, but is it? Or is there more to it?

Photo Credit. Bertinet, Richard. "Pâte au seigle (Pâte d'olives)." Pains gourmands: 50 recettes simples et créatives [1]. Paris: Larousse, 2006. 123. Print.