Preheat oven to 400°F. Grease the bottom and up the sides of a 2-cup deep soufflé dish with butter and sprinkle 1½ tsp erythritol to coat all buttered areas. Set aside.

Melt the chocolate in a small bowl in a microwave at 30 second intervals until melted through. Do not overheat and stir between intervals.

In a medium bowl whisk 2 egg yolks with 1 tbsp warm water, 1 tsp vanilla, ¾ tsp ground cinnamon and ⅛ tsp cayenne pepper (add more if more spice is desired). Add the melted chocolate and whisk until incorporated and smooth. Set aside.

In a medium bowl, whip the egg whites with 2½ tablespoons erythritol and a large pinch of stevia to stiff peaks. Whisk a few tablespoons of the egg whites into the chocolate mixture, then quickly but gently fold in the remaining egg whites until a lighter airy mixture results and all ingredients are blended (do not over blend or you will deflate the egg whites).

Pour into the souffle dish and bake on a sheet pan for 15-18 minutes. The souffle will rise over the top of the dish and it should appear slightly jiggly but not wet in the center when shaken. Serve immediately.