Prepare the date caramel first. Cover the pitted Medjool in hot or boiling water for at least 30 minutes. Once soft, scoop out 1/4 cup of the soaking water and set aside. Drain the dates, and transfer them to a food processor. Add the soaking water and vanilla extract. Process until creamy, scraping down the sides of the food processor as you need to. Transfer the date caramel to a medium bowl until ready to use.
Make the chocolate. In a microwaveable safe bowl, combine the chopped dark chocolate and coconut oil. Microwave for 50 seconds to 1 minute. Remove the bowl and stir until creamy (chocolate may appear to not have fully melted, but once you stir, it will combine with the hot coconut oil). Add the powdered monk fruit and granulated monk fruit and stir again until everything is blended.
Pour 1-2 tablespoons of the melted chocolate into the bottom of the candy bar mold. Transfer the mold to the freezer to harden for at least 30 minutes. Set the remaining melted chocolate aside.
Make the butter cream frosting. In a large bowl, combine the grass-fed butter and coconut oil. Beat with a hand mixer, immersion blender with whisk tool or a large whisk until fluffy, about 30 seconds to 1 minute. Add the powdered monk fruit and vanilla extract and beat again until everything is blended together, using a spatula to scrape down the sides of the bowl as you need to and beat again.
Once the chocolate has set in the bottom of the bar mold, layer in the date caramel and buttercream filling (about 1-2 tablespoons each mold). Pour the remaining melted chocolate over the filling in equal amounts until used up. Place the mold back in the freezer to completely set, at least 1 hour.