Chocolate liquor and erythritol, on their own, will not work. And this isn't a case of it'll-be-okay-but-not-great. It will be inedible. This is because erythritol has very little sweetness, and, undissolved, it has a notoriously unnerving cooling effect (almost like mint), and, in a water free environment like a chocolate bar, it's almost impossible to dissolve (on it's own).
Erythritol really doesn't work as a sole sweetener, ever. This is why you'll never find a commercial product sweetened only with erythritol. You'll always find it with other things- like polydextrose and inulin (sometimes called 'dietary fiber' - these help keep the erythritol dissolved) and high intensity sweeteners. Erythritol plays a role- desserts typically are better with it, than without, but it's not the star, it's not even a supporting actor. It's an extra. And if you try to shoehorn it into a larger role, it's incredibly unforgiving.
This is a slightly more knowledgeable attempt at low carb chocolate than most,
https://www.wholesomeyum.com/low-carb-keto-chocolate-bar-recipe/
but they really don't grok the concept of dissolving the erythritol and the inulin. Heat is not enough. This is why you see little white specks of undissolved sweeteners in the chocolate. They also don't add a high intensity sweetener. I think, with the inulin and the cocoa butter, this might be edible, but I doubt many people would find it good. And the texture, as you can see, is pretty far from ideal. But the bottom line is that, unless you can keep erythritol dissolved, it's going to taste horrible.
How do sf chocolate bar manufacturers dissolve erythritol and keep it dissolved? I don't know. My best guess is that they melt the erythritol and inulin in water and cook it into a hard ball glass, then pulverize it and add that to the chocolate. But that's just a guess. Whatever it is, it serious food chemistry that you might want to avoid.
If you have the erythritol and the chocolate liquor... I'd probably go the ganache route. Get yourself some polydextrose or inulin, some heavy cream and a high intensity sweetener.
On the topic of high intensity sweeteners... stevia is okay for tea, but the strong sweetening requirements of dark chocolate are too much for it. It's not going to taste right. If you score some cocoa butter and go with a milk chocolate ganache, you'll lessen the amount of sweetener you'll require and maybe move in a more stevia friendly direction (or maybe monk fruit), but, if you truly want a decent quality of sweetness, nothing's going to touch artificial sweeteners. Splenda will take you a huge distance, but splenda and something else (like acesulfame potassium or possibly aspartame) will take your quality of sweetness even further.
One caveat. Polysaccharides (inulin/poydextrose) can be laxating. But they typically aren't as laxating as maltitol and, imo, more importantly, they don't spike GI like maltitol does. But, if you're going to work with erythritol, you can't avoid them. They're just about the only thing that keeps erythritol from crystallizing into a cooling nightmare.
