1-First step: Separate and prep the eggs Start with cold eggs, because the yolks and whites separate more cleanly when chilled. Crack each egg and place the whites in a large, clean bowl and the yolks in a smaller bowl. A clean bowl matters here because any grease can stop the whites from whipping properly. Let the egg whites sit at room temperature for a short while before whipping so they rise better.

2-Second step: Whisk the yolks Whisk the yolks until they look smooth and even. You are not trying to make them fluffy, just uniform. This small step helps them blend smoothly later with the whipped cream, which is what keeps the mousse from turning lumpy or streaky.

3-Third step: Melt the chocolate and butter Place the broken chocolate and butter in a microwave-safe bowl. Heat in 20-second bursts, stirring after each burst until the mixture is smooth. Stop as soon as it melts, because overheated chocolate can seize up and become grainy. Let it cool to room temperature, but keep it runny. The chocolate should still be pourable, around 35 to 40°C or 95 to 104°F.

4-Fourth step: Whip the cream In a separate bowl, whip the full-fat cream to stiff peaks. You want the peaks to stand up, but do not keep going so long that the cream starts turning into butter. If you are using thickened cream, watch it closely, because it can move from perfect to over-whipped fast. A chilled bowl helps if your kitchen is warm.

5-Fifth step: Beat the egg whites with sugar Add the caster sugar to the egg whites and whisk until firm peaks form. The tip should have a slight flop, often called a floppy elf hat consistency. That funny little image is actually a very useful clue. It means the whites are strong enough to support the mousse but still soft enough to fold in easily.

6-Sixth step: Fold the yolks into the cream Use a rubber spatula to gently fold the egg yolks into the whipped cream. Keep the motion light, lifting from the bottom and turning over the mixture. Up to eight folds is usually enough. You want the mixture combined, not flattened.

7-Seventh step: Add the melted chocolate Check that the chocolate is still pourable before mixing. If it has thickened too much, warm it very briefly until it loosens again. Fold the chocolate into the cream and yolk mixture using gentle, careful strokes. Again, think lifting and turning, not stirring like you are late for dinner. About eight folds should do it.

8-Eighth step: Lighten the base with egg whites Fold about one-quarter of the beaten egg whites into the chocolate mixture first. This lightens the base and makes the next addition easier. Then fold in the rest of the whites slowly until no white streaks remain. Try to stop at around 12 folds max. The goal is a mousse that stays airy, not one that gets beaten into submission.

9-Ninth step: Portion and chill Spoon the mousse into 4 small serving dishes or glasses. Cover and refrigerate for at least 6 hours, though overnight is even better. That chilling time helps the mousse set into its dreamy, spoonable texture. If you are making this for guests, it is a great make-ahead dessert because the fridge does all the finishing work.

10-Tenth step: Garnish and serve Top the set mousse with whipped cream and chocolate shavings. For a little color, add fresh raspberries or a mint leaf. This turns a simple mousse recipe into something that feels restaurant-worthy without much effort.