Ingredients :

• Cocoa powder — Use unsweetened cocoa, not hot chocolate powder like Nesquik. The difference in taste is huge. Basic Van Houten works perfectly. Two tablespoons are enough: we are looking for a balance with the vanilla, not a disguised chocolate cake.
• Vegetable oil — This is the secret to long-lasting moistness. Melted butter gives a denser texture that firms up as it cools. Oil remains liquid even when cold—keeping the cake soft the next day, and even the day after. Use sunflower or rapeseed oil, neutral in taste. Absolutely no olive oil.
• Vanilla extract — Two teaspoons, and real vanilla if possible—not artificial vanillin aroma that smells like heated plastic. The difference is clearly noticeable once baked. A small bottle from your supermarket’s organic brand is more than enough.
• Warm milk (to dissolve the cocoa) — Warm milk dissolves the cocoa without lumps and allows it to be easily incorporated into the batter. Two tablespoons are enough. Warm water works just as well if you don’t have milk on hand.