1. Pre-heat oven to 450F (conventional, no fan)
2. Prepare 5 muffin cups in a non-stick jumbo muffin pan, or 5 8oz ramekins, by generously brushing them with softened butter and then dusting with cocoa powder. Shake out any excess cocoa powder and clean the edges (otherwise the excess cocoa powder on the edges or on the muffin pan can burn and create smoke in the oven)*
3. Place the chopped dark chocolate and unsalted butter in a microwave safe bowl. Microwave in 20 second increments, stirring in between, until the chocolate and butter are fully melted and mixed together. Set aside
4. In a separate bowl, add the eggs, egg yolks and sugar. Whisk on medium-high speed for ~3 minutes until the mixture becomes really light in color, thick, fluffy and ribbony. It should almost triple in volume
5. Pour the chocolate mixture into the egg mixture, and whisk on medium-low speed just until combined. Do not overmix
6. Sift in the flour and salt. Use a rubber spatula to very gently fold the dry ingredients into the batter, taking care not to overmix
7. Divide the batter evenly between the 5 prepared muffin cups or the ramekins. The batter will almost reach the top with a little margin left**
8. Bake in the pre-heated oven for 8-10 minutes if using the muffin tray, or 10-12 minutes if using the ramekins. Be sure to keep an eye on the cakes and look for signs of doneness. They are done baking when the top looks set and the edges pull away from the pan, but the cakes still jiggle when lightly shaken. You can also insert a toothpick in the middle to ensure it is molten but not completely liquid / raw
9. Remove the cakes from the oven. Rest them for 1 minute, then use a butter knife to gently separate them from the edges of the muffin cups / ramekins. Carefully flip the cakes out of their molds; they should come out easily
10. Serve hot with a dusting of powdered sugar and / or a scoop of vanilla ice cream. You can even drizzle over some chocolate fudge sauce. Enjoy!

Video tutorial: