Preheat the oven to 350°F (175°C). Grease 4 ramekins or line them with parchment paper.
In a microwave-safe bowl, melt butter and sugar-free chocolate together in 30-second intervals, stirring between each, until smooth.
In a separate bowl, combine almond flour, cocoa powder, and sweetener.
In another bowl, whisk together eggs and vanilla extract until smooth. Slowly add the melted chocolate mixture and stir well to combine.
Add the wet mixture into the dry ingredients, stirring until a smooth batter forms.
Divide the batter evenly among the greased ramekins, filling them about 3/4 full.
Bake for 10-12 minutes, until the edges are set but the center is slightly jiggly.
Let the cakes cool for 1-2 minutes, then run a knife around the edges. Invert the ramekin onto a plate to serve.
Serve immediately with whipped cream, berries, or keto ice cream.