Chocolate lava cake with a gooey molten center. These individual cakes are baked just long enough for the outer layer to set while the centers remain soft.
Preheat the oven to 450°F. Generously grease or butter four 6-ounce ramekins then lightly dust them with cocoa powder. Place the ramekins on a baking sheet and set aside.
Add chocolate and butter to a medium-sized microwave-safe bowl and heat in 15-second intervals, stirring after each one, until chocolate is fully melted and smooth. Set aside.
In a medium bowl, beat the eggs and yolks with an electric mixer on medium speed until frothy, pale in color, and almost doubled in volume, about 2 minutes.
With the mixer running, gradually add the sugar, followed by the vanilla, salt, and espresso powder.
Pour the melted chocolate into the egg mixture and fold with a silicone spatula until well combined.
Add the flour and gently fold until no clumps of dry flour are visible.
Divide the batter evenly between the 4 ramekins and bake for 10-11 minutes, until the edges are set and puffed but the centers are soft and jiggly.
Allow the cakes to cool for 1 minute then run a knife or offset spatula around the edges to loosen from the pan. Invert the ramekins onto individual serving plates and let sit until the cakes release, about 1 minute.
Lift the ramekin off and top with your choice of toppings. Serve immediately.
Notes
Chocolate: You can use bittersweet or semisweet chocolate. Unsweetened chocolate will require more sugar but this can throw off the chemistry of the recipe. Avoid using chocolate chips. They don't melt as smoothly and can give you different results than desired.
Eggs: The eggs must be at room temperature. Place them in a bowl of warm water for about 5 minutes to quickly bring them to room temperature. Use the 2 leftover egg whites to make macarons, classic chocolate mousse, or macaroons.
Espresso powder: There isn't enough in the recipe to make it taste like espresso/coffee. It only enhances the chocolate flavor and it's completely optional. Leave it out if you don't wish to use it.
Flour: Be sure to sift the flour to remove any clumps. This will make it easier to mix into the batter without deflating it.
Undercooked centers: Lava cake is more than just undercooked cake. The unique chemistry makes it more of a cross between souffle and cake with a custard center. The runny center should reach 160°F during baking which makes it safe to eat. You can use an instant-read digital thermometer to check the internal temperature.
No ramekins? No problem! Prepare 6 cups of a 12-cup muffin pan by greasing them and dusting with cocoa powder. Bake at 450°F for 7-9 minutes.
Make ahead tip
Lava cakes are best immediately after they are baked.
Unbaked cakes can be refrigerated for up to 8 hours before baking. Let sit at room temperature for 30 minutes before baking.
Unbaked batter can also be frozen in the ramekins to bake later. Thaw them at room temperature for about an hour then bake as instructed. You may need to add an additional minute or two to the bake time so watch them closely.