Ingredients :

• The Cheese — This is what does the work. A good cheddar aged 12 months brings tang and melts well. Gruyère provides the stretch you’re looking for. Avoid mozzarella on its own — too bland, too much water. A 70% cheddar / 30% gruyère mix works very well.
• The Flour — All-purpose (T45 or T55), classic. What really matters: weighing it to the gram rather than using an approximate spoon — it changes the final texture significantly.
• The Butter — Melted and cooled, not hot. If you add it scalding to the dough with the eggs, you risk cooking them before you even get to the oven. Semi-salted butter adds a very interesting salty base.
• The Eggs — Two whole eggs for structure and richness. They bind the dough and give it that slightly golden hue inside. Use them at room temperature — the dough will be more homogeneous.