Preheat your oven to 425°F (220°C). Lightly grease ramekins with butter or non-stick spray.

In a microwave-safe bowl or double boiler, melt the sugar-free chocolate and butter together. Stir until smooth and glossy. Allow the mixture to cool slightly.

In a separate bowl, whisk the eggs with the keto sweetener until pale and slightly thickened.

Slowly pour the melted chocolate mixture into the egg mixture while whisking continuously to avoid scrambling the eggs.

Sift in almond flour, cocoa powder, salt, and espresso powder (if using). Fold gently until just combined.

Stir in vanilla extract until fully incorporated.

Divide the batter evenly among prepared ramekins, filling each about three-quarters full.

Place ramekins on a baking tray and bake for 9–12 minutes. The edges should be set, but the center should remain soft.

Let the cakes rest for 1–2 minutes before serving.