Any fat, even a bit of cream on the whisk, will stop them whipping. If unsure, wipe the bowl and whisk with lemon juice or vinegar and dry. | Cold yolks + hot chocolate = splitting. Aim for both to be warm or at room temp so they combine smoothly. | The water should be simmering, not boiling. Keep the bowl just above the water and whisk constantly to avoid scrambling. | The sabayon is ready when it thickens and leaves a light trail, not just after a set time. | Give it 2-3 minutes after melting. Too hot and it can cook the yolks or turn grainy. | Over-whipped cream or egg whites make the mousse heavy and harder to fold. Stop when they just hold their shape. | Always mix a spoon of cream into the chocolate first. This makes folding the rest much easier and keeps the air in. | Use a spatula, scoop from the bottom, turn over, and rotate the bowl. This keeps the mousse light. | Once it looks combined, stop. Overworking it knocks out the air you just built. | Chill until just set, not rock hard. If it firms up too much, let it sit out 15-20 minutes before serving. | Use a good olive oil, fruity and smooth. It should taste good on its own. | Keeps in the fridge for up to 2 days and will firm up slightly. | Let it sit out for 15-20 minutes before serving for best texture. | Great layered with fruit or spread onto warm pancakes.