1. Preheat your oven to 175°C. Grease two ramekins or oven-safe dishes with butter or cooking spray.
2. In a small bowl, whisk together the almond flour, cocoa powder, powdered erythritol, baking powder, and salt until well combined.
3. In a separate larger bowl, whisk together the melted butter, egg, and vanilla extract until smooth.
4. Gradually add the dry ingredients to the wet ingredients, stirring well after each addition, until you have a smooth batter.
5. Place half of the batter into each of the prepared ramekins, making sure they are evenly filled.
6. Place the chopped dark chocolate in the center of each ramekin, gently pressing it down into the batter.
7. Bake in the preheated oven for about 12-15 minutes, or until the edges are set but the center is still slightly jiggly.
8. Remove from the oven and let the lava cakes cool in the ramekins for a couple of minutes.
9. Gently run a knife around the edges of each ramekin to loosen the cakes. Carefully invert the ramekins onto serving plates or bowls to release the lava cakes.
10. Serve warm with optional toppings like whipped cream, berries, or a sprinkle of powdered erythritol. Enjoy your delicious chocolate keto lava cake!