Preheat oven to 200°C. Grease 4 ramekins (measuring about 10cm in diameter).
Melt butter and chocolate in a small pot on low heat. Stir to combine, remove from heat and set aside. Alternatively, melt in microwave for 20 second bursts and stir to combine.
In a medium bowl, add eggs, egg yolks, sugar and salt. Use an electric beater or whisk to beat until pale and fluffy, about 4 minutes. Using a spatula, gently fold in the chocolate mixture. Gently fold in the flour, until combined.
Divide mixture evenly between ramekins. Bake for 15-17 minutes, until cooked but still gooey in the middle.
While lava cakes bake, add cream to a medium bowl and use electric beaters (or a whisk) to beat until fluffy, about 2-4 minutes.
Cut around the edge of ramekins and flip each lava cake into a bowl, or simply eat straight from the ramekin! Top with a dollop of whipped cream.