Prep the ramekins. Heat oven to 400°F (205°C). Generously butter two 6-ounce ramekins and dust the insides with cocoa powder. Tap out the excess. This helps the cakes release cleanly and protects the edges from sticking.

Melt chocolate and butter. In a heatproof bowl, combine the chocolate and butter. Melt in the microwave in 20–30 second bursts, stirring between each, until smooth. You can also melt over a double boiler. Let it cool for 2 minutes so it doesn’t scramble the eggs.

Whisk the eggs and sweetener. In a separate bowl, whisk the egg, egg yolk, and powdered sweetener until slightly pale and thickened, about 30–45 seconds by hand. This adds a bit of lift and tenderness.

Combine the mixtures. Whisk the vanilla and salt into the melted chocolate. Gently stream the chocolate mixture into the egg mixture while whisking. If using, stir in the heavy cream.

Add dry ingredients. Sift in the almond flour and cocoa powder. Fold gently with a spatula until just combined. The batter should be glossy and pourable, not runny.

Fill the ramekins. Divide the batter evenly between the two prepared ramekins. For a more dramatic lava effect, you can add a small square of sugar-free chocolate to the center and cover it with batter.

Bake. Place ramekins on a baking sheet and bake for 8–10 minutes. The edges should look set, but the centers should still jiggle. Do not overbake or the centers will set fully.

Rest and unmold. Let the cakes rest for 1 minute. Run a thin knife around the edge. Invert onto plates, give a gentle shake, and lift the ramekin. If you prefer to eat straight from the ramekin, that works too.

Finish and serve. Top with a dollop of sugar-free whipped cream or a few berries. Serve immediately for the best lava flow.

Air fryer option. Preheat air fryer to 375°F (190°C). Air fry for 6–8 minutes in heat-safe ramekins. Watch closely from minute 6 onward.