This is a classic mousse which means there is no cooking of ingredients involved. If you are one of those people with issues about raw eggs - umm scroll back and find the chocolate pudding post and make that instead. Sorry but for me it's real mousse or nothing.
A quick note about chocolate. Of course, always use the best chocolate you can buy. But for this and many other recipes calling for dark chocolate, be careful about using a high % chocolate. I tried this recipe with my usual 70% dark chocolate and it was too intense and concentrated. I'd stick with the 60% range or so for this particular recipe or use less chocolate.
2 egg yolks
4 egg whites
7 oz dark chocolate
2 oz caster sugar (US: superfine sugar if possible)
1 teaspoon golden syrup/maple syrup/light corn syrup
½ cup double cream
1 oz unsalted butter
1 TBs espresso or strong coffee or cognac or rum
1 tsp vanilla
1. Use a large pyrex measure/mix bowl with handle for this ideally. Break up the chocolate and place in the bowl with the syrup and butter.
2. Nuke for 60 seconds in microwave. Remove from microwave and stir gently to make sure all the chocolate is melted - the residual heat will melt all the remaining bits quickly. Set aside to allow to cool slightly while you start the next step.
3. Whisk the egg yolks and the cream together, add vanilla and a good splash of espresso or cognac.
4. Take the bowl of melted chocolate and gently stir in the cream and egg yolk mixture until they have combined.
5. Put the egg whites into a large bowl and whisk them with an electric hand whisk until they have reached the soft peak stage (when the whisk is taken out of the egg whites the peaks left by the whisk should be limp and rounded).
6. Pour the sugar over the egg whites and then continue to whisk them until they reach the stiff-peak stage (when the whisk is removed from the egg whites, the peaks left by the whisk should be pointed and firm.
7. Spoon about half of the whisked egg whites into the chocolate mixture and gently fold it in using a spatula (I love silicone for this!) until it is completely combined.
8. Add the rest of the egg whites and fold them in until they have completely combined (Don't beat or stir the mixture as this will break the bubbles in the egg whites, resulting in a heavy mousse).
9. Either put the whole bowl into the fridge or pour the mixture into ramekins/cups for individual portions and put them into the fridge. Cover with saran/cling film, of course.
10. Let the mousse set in the fridge for at least 2 hours before serving. Overnight is fine.
The mouse will keep in the fridge for up to 3 days (are you insane, what kind of household lets mouosse sit uneaten that long?)
You can serve as is or with a dollop of whipped cream on top.