Ingredients :

• Softened butter — 120 g, and truly soft — not melted, not still cold from the fridge. Taken out 1 hour before. This is what gives the melting texture and the characteristic buttery aroma. Semi-salted butter works very well here, in which case you can skip the pinch of salt.
• Chocolate squares (for the core) — One square per cookie. This is where you can have fun: 70% dark chocolate for something intense, milk chocolate for something sweeter. Lindt or Nestlé Dessert squares hold up well during baking without disappearing completely into the dough.
• Chocolate chips — 100 g in the dough to double the chocolate pleasure. Real baking chips melt better than roughly chopped bar pieces — you can taste the difference.
• Sugar — 100 g of classic white sugar. You can replace half with brown sugar for a deeper flavor, a slight note of molasses that pairs beautifully with chocolate.