Preheat oven to 375°F.

Generously grease four 6-ounce custard cups with butter and dust with xylitol. Place cups on a baking sheet.

Place butter and chocolate in a double boiler over medium heat and cook until just melted, about 3 minutes (or 1 minute in a microwave on high). Remove from heat and let cool to room temperature.

Pour chocolate mixture into a large bowl; add almond flour and stir until just combined. Set aside.

In a large bowl, beat eggs, egg yolks, xylitol and vanilla with an electric mixer on high speed until almost firm peaks form, about 4 minutes.

In three additions, fold egg mixture into chocolate mixture.

Divide batter in cups. Bake 8-9 minutes until a toothpick inserted near edge comes out clean and inserted in center comes out with some batter.

Cool 3 minutes. Run knife around edge, turn upside down to release onto serving plates. Serve immediately. Makes 4 servings.