Combine chocolate and cocoa butter in a double boiler or chocolate melter. Heat until all the chocolate and cocoa butter is melted.
Add the powdered milk, powdered stevia, and powdered erythritol. Stir until all the powdered ingredients have dissolved and mixture is smooth. It may take a while to dissolve all the erythritol.
Mix in vanilla extract after removing from heat. Pour melted chocolate into candy bar mold.
Let cool in refrigerator or freezer. Once set, remove from mold. Store in covered container. Can also be stored in refrigerator or freezer, if desired.
Notes
Stevia extract powder can be used in place of the monk fruit extract powder.Monk fruit can be increased in small amounts if a sweeter chocolate is desired. A small amount of monk fruit or stevia can also be used in place of the erythritol if desired.Heavy cream powder can be used in place of the low-carb milk powder.