Preheat your oven to 425°F / 220°C and grease 4 large ramekins with baking grease. Place the ramekins on a sheet tray and set aside.

Place the butter and chocolate in a microwave safe bowl and microwave for 1 minute.

Whisk the butter and melted chocolate together until smooth and completely melted.

Microwave for another 15 seconds if needed to make sure both ingredients are completely melted.

Stir the sugar into the melted chocolate and butter mix and then whisk in the eggs and egg yolk.

Add the vanilla and whisk well so the batter is smooth.

Whisk in the flour, making sure there are no lumps.

Divide the batter between the prepared ramekins and then bake in the preheated oven for about 12-14 minutes. The sides of the cakes should be set but the center will still be soft.

Remove the cakes from the oven and let sit for just one minute then serve while still hot and gooey!