Place 2 chocolate bar silicone molds on a flat board or plate. I recommend placing a piece of parchment paper between the mold and the plate. This prevents the silicone mold from sticking to the plate when you freeze the bar later in the recipe. Set aside.
In a small saucepan, under medium heat, melt the cocoa butter.
When fully melted, remove the saucepan from the heat and stir in stevia drops, powdered sweetener (not crystal! you don't want bits in your chocolate), and salt.
Return to medium heat until cocoa butter slightly boils and reaches 250°F (121°C), it's the temperature at which the erythritol will dissolve and prevents a gritty texture in your chocolate.
Remove from heat and stir in unsweetened cocoa powder.
Stir quickly and immediately transfer the liquid into the 2 silicone mold to fill them up to the top. Working quickly prevents the cocoa powder and cocoa butter from separating and creates the most consistent bars.
Freeze 10 minutes or until the chocolate bars are hard and fully set
Remove from the freezer, flip over the chocolate mold onto a flat surface and peel off the mold from the bar to release.
Store the chocolate bars in the fridge in an airtight box or at room temperature. The melting point of cocoa butter is 93°F (34°C), so if your house is not that warm, the chocolate bars won't melt in the pantry.
No silicone mold?
You can pour the chocolate mixture into a 9-inch x 5-inch loaf pan (halve the recipe first, freeze, release, then repeat as the recipe makes 2 chocolate bars). Make sure you cover the pan with parchment paper, grease the paper with oil spray.
Keto chocolate toppings
Before freezing the bars, you can add some crunchy keto toppings like sliced/chopped almonds, toasted coconut flakes, chopped brazil nuts, pecan, and freeze-dried raspberries.
One chocolate bar has 24 chocolate squares. This recipe makes 2 chocolate bars, so 48 chocolate squares. Serving size is 4 squares. Therefore one chocolate bar has 6 servings, 12 serving for the whole recipe.I recommend using this silicone chocolate mold for best result (affiliate link)